The Greenland White-fronted Goose Anser albifrons flavirostris€¦ · Birds breeding in the north...

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National Environmental Research Institute Ministry of the Environment . Denmark The Greenland White-fronted Goose Anser albifrons flavirostris The annual cycle of a migratory herbivore on the European continental fringe Doctor’s dissertation (DSc) Anthony D. Fox

Transcript of The Greenland White-fronted Goose Anser albifrons flavirostris€¦ · Birds breeding in the north...

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National Environmental Research InstituteMinistry of the Environment . Denmark

The GreenlandWhite-fronted GooseAnser albifrons flavirostrisThe annual cycle of a migratory herbivore on theEuropean continental fringe

Doctor’s dissertation (DSc)

Anthony D. Fox

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National Environmental Research InstituteMinistry of the Environment . Denmark

The GreenlandWhite-fronted GooseAnser albifrons flavirostrisThe annual cycle of a migratory herbivore on theEuropean continental fringe

Doctor’s dissertation (DSc)2003

Anthony D. FoxDepartment of Coastal Zone Ecology

Denne afhandling er af det Naturvidenskabelige Fakultet vedKøbenhavns Universitet antaget til offentligt at forsvares for dennaturvidenskabelige doktorgrad. København den 14. marts 2003.

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Data sheet

Title: The Greenland White-fronted Goose Anser albifrons flavirostrisSubtitle: The annual cycle of a migratory herbivore on the European continental fringe

Doctor’s dissertation (DSc)

Author: Anthony D. FoxDepartment: Department of Coastal Zone Ecology

Publisher: Ministry of the EnvironmentNational Environmental Research Institute

URL: http://www.dmu.dk

Date of publication: February 2003

Technical editor: Karsten Laursen

Financial support: No external support.

Please cite as: Fox, A.D. 2003: The Greenland White-fronted Goose Anser albifrons flavirostris.The annual cycle of a migratory herbivore on the European continental fringe.Doctor’s dissertation (DSc). National Environmental Research Institute, Denmark.440 pp.

Reproduction is permitted, provided the source is explicitly acknowledged.

Layout: Helle Klareskov

ISBN: 87-7772-719-3

Paper quality: Cyclus PrintPrinted by: Schultz Grafisk

Environmentally certified (ISO 14001) and Quality certified (ISO 9002)

Number of pages: 440Cirkulations: 500

Price: DKK 200.- (incl. 25% VAT, excl. freight)

Internet-version: The report is also available as a PDF-file from NERI’s homepagehttp://www.dmu.dk/1_viden/2_publikationer/3_oevrige

For sale at: Ministry of the EnvironmentFrontlinienStrandgade 29DK-1401 København KTel. +45 32 66 02 [email protected]

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Contents

Summary ......................................................................................................................... 5

Dansk resumé................................................................................................................. 9

1 Introduction ..................................................................................................... 11

2 Limits to population size in recent historical times ................................ 17

3 Accumulation of body stores and the flight to Iceland .......................... 27

4 Spring staging in Iceland and the flight to Greenland ........................... 35

5 Pre-nesting feeding ........................................................................................ 43

6 Reproduction ................................................................................................... 47

7 Moult of flight feathers ................................................................................. 59

8 Survival ............................................................................................................. 65

9 Synthesis ........................................................................................................... 73

10 Acknowledgements ........................................................................................ 87

11 References ........................................................................................................ 92

12 Appended manuscripts ............................................................................... 101

Appendix 1: Statistical endnotes ............................................................................ 427

Appendix 2: Future Research Priorities ................................................................ 433

National Environmental Research Institute

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The Greenland White-fronted Goose Anser albi-frons flavirostris is the most morphologically dis-tinct sub-species of the circumpolar White-fronted Goose Anser albifrons. The populationbreeds in West Greenland and migrates throughIceland to winter in Britain and Ireland. After aperiod of population decline from the 1950s tothe 1970s, protective legislation enacted on thewintering grounds in the early 1980s removedwinter hunting as a source of mortality andpopulation size doubled to the present level of30-35,000, although numbers have fluctuated invery recent years. Declines and extinctions atsome wintering resorts continue, despite thenature conservation objective of maintaining thecurrent geographical range of the population.Most research effort has concentrated at the twomost important wintering sites, Wexford Slobsin southeast Ireland and the island of Islay offsouthwest Scotland. These two resorts have sup-ported some 60% of the total population in re-cent years. Irish wintering geese tend to stage inwestern Iceland and breed in the north of therange in Greenland, whilst Scottish birds tendto use the southern lowlands of Iceland andbreed further south.

Greenland White-fronted Geese habitually feedthroughout the annual life cycle on the lower stemof the common cotton grass Eriophorum angusti-folium, which they extract from soft substrates inpeatland ecosystems. The restricted extent of pat-terned boglands (which formed the traditionalwinter habitat) would undoubtedly have con-strained population size, even in a landscapeunchanged by Man’s activities. Exploitation ofthis highly specific food in a restricted habitat isalso likely to have shaped its highly site-faithfulhabit and influenced the evolution of the unusu-ally prolonged parent-offspring relationshipswhich distinguishes this population from mostother geese. During the last 60 years, the race hasincreasingly shifted from feeding on natural veg-etation habitats to intensively managed agricul-tural grasslands, which in some areas has broughtthe population into conflict with agriculture. De-spite this change in habitat use, there has been norange expansion, since new feeding traditionscontinue to be associated with use of long estab-lished night time roost sites.

Consistent with providing advice to support themost effective conservation management for thepopulation, the broad aim of the analysis presentedhere is to begin to identify factors that could po-tentially limit this population or regulate the rateof change in its numbers. Given that geese are suchsocial animals, it is especially interesting to exam-ine how individual behaviour could influence sur-vival and reproduction, and how this scales up tochanges in the overall population.

This thesis therefore examines the annual life cy-cle of the Greenland White-fronted Goose, con-centrating on periods of nutritional and energeticneed (e.g. migration, reproduction and wingfeather moult) and the way in which individualsmay balance their short and longer-term budg-ets. Body mass and field assessments of fat storeswere used as relative measures of body condi-tion (taken to represent the ability of an individualto meet its present and future needs). GreenlandWhite-fronted Geese maintained body massthrough mid winter but accumulated mass in-creasingly until mid April when they depart forIceland. Assuming 80-90% of this accumulationis fat, departing geese had more than enough fuelfrom such energy stores to sustain this springflight. The majority of this mass was depleted enroute to Iceland where they staged for anotherc.15 days prior to the journey onwards to Green-land. Here, geese increased body mass by 25-30grams per day. In total, this is slightly less thanthat during December-April but accumulatedover a considerably shorter period. Most Green-land White-fronted Geese attained these highrates of mass accumulation on artificially man-aged hayfields although they fed also on adja-cent wetlands. The three most common grass spe-cies exploited showed differences in profitabilitybecause of differing leaf densities, growth ratesand nutrient quality - all of which affected foodintake rates and hence the rate of accumulationof stores by geese. Behavioural dominance is amajor determinant of access to best food resourcesin this population. Since individual geese showeddifferent levels of feeding specialisation on thethree grass species there is the potential for den-sity effects and social status to influence rates ofnutrient acquisition in Iceland that could affecttheir future fitness.

Summary

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Arrival mass in West Greenland confirmed thatgeese lost more mass flying from Iceland toGreenland than during the same flight distancefrom Iceland to Ireland. The difference was con-sistent with the predicted extra costs required tocross over the Greenland Ice Cap. After arrival,breeding geese fed intensively for a period of 10-14 days during which mass accumulation for in-vestment in reproduction occurred at the samerapid rate as in Iceland. Female geese protectedby attendant ganders were able to exploit a richfood supply (storage organs of plants) duringuninterrupted periods of foraging. Nest densitieswere low and nest habitat apparently unlimited,so it seems unlikely that breeding habitat per selimits breeding numbers. More likely, the extentand availability of pre-nesting feeding habitatsin the central part of breeding range could limitpre-nesting accumulation of stores. This wouldpotentially limit the numbers of individual fe-males attaining adequate body stores to achievesuccessful reproduction. Hence, increasing goosedensities exploiting a finite pre-nesting food re-source may increasingly limit the numbers ofgeese attaining a level of body condition suffi-cient to enable successful reproduction. Birdsbreeding in the north of the summer range stagefurther south in Greenland (where they competefor resources with locally nesting birds) beforemoving north. Global climate change models pre-dict that the northern breeding element of thepopulation will face continuing reductions insummer temperature. In addition, northern breed-ing birds will encounter greater goose densitiesin southern spring areas with which they mustcompete for spring food resources.

Despite the recent increase in total population sizeunder protection, the absolute numbers of suc-cessfully breeding pairs returning with young tothe two most important wintering areas havebeen more or less constant. This suggests thatsome finite resource limitation may now operate(most likely on the breeding grounds), restrict-ing recruitment. Amongst known age markedindividuals, the probability of survival to success-ful breeding had fallen from 15% amongst gos-lings hatched in 1983 to 3% amongst those from1992 and the mean age of first breeding increasedfrom c.3 years prior to 1988 to c.5 years of age insubsequent cohorts. The proportion of potentiallybreeding adults returning with young to the win-tering areas is falling at both the wintering sitesat Wexford and Islay, but the faster rate of declineat Wexford has had a greater effect and is now

causing a decline in wintering numbers there. Itmay be that the cooling of the climate in NorthWest Greenland and increasing densities furthersouth are already affecting the Wexford winter-ing birds. At the same time, the Islay winteringbirds that tend to nest further south, benefit fromimprovements in spring climate conditions incentral west Greenland.

Greenland White-fronted Geese moult flightfeathers at amongst the lowest levels of bodymass and showed no change with moult stage,suggesting they meet energetic and nutrient de-mands from exogenous sources. However, con-finement of the flightless geese to the proximityof water to escape predation constrains totalavailable habitat. Newly colonising CanadaGeese have increasingly exploited the samemoult sites and are behaviourally dominant overWhitefronts. Dramatic increases in the numbersof Canada Geese (which winter in NorthAmerica) suggest the potential for increasingconflict on the breeding areas between the twospecies in future.

The increase in numbers since protection fromwinter hunting at Wexford is consistent with aconstant apparent annual adult survival since the1960s but the relative stable numbers before 1982seem to have been maintained by the balancebetween hunting kill and breeding success. Im-mediately following protection (i.e. in the absenceof apparently additive hunting mortality), num-bers increased at rates regulated by the potentialof reproduction to replace lost individuals. Sincethe early 1990s, Wexford numbers have declineddue to falling fecundity and to a catastrophic lossof first-year birds and their parent adults in onesingle year. Hence, reductions in reproductiveoutput now seem to be limiting Wexford num-bers. Since fecundity has also declined on Islayand some other winter resorts, this appears to bea general phenomenon in the population as awhole at this time. On Islay, reductions in the re-production rate have yet to halt the linear increasein numbers since protection.

It would therefore appear that the population waslimited prior to the 1980s by hunting mortality.Under protective legislation, the population ex-panded to reach a new equilibrium level set bylimits to reproduction. Given the predicted effectsglobal climate change, the increases in goose den-sity and the colonisation of the breeding areas byCanada Geese, the future conditions affecting

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Greenland White-fronted Geese are unlikely toremain as they are now. The results of many yearsmonitoring are reviewed in the light of the con-

servation issues facing this population in the fu-ture and recommendations are made for futureresearch.

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Den grønlandske blisgås Anser albifrons flavirostrisyngler i Vestgrønland og trækker via Island til over-vintringsområder i Storbritannien og Irland. Sidenjagtfredningen i vinterkvartererne i 1980erne erbestanden steget fra 14,300-16,600 i 1970erne tilmellem 30,000 og 35,000 individer i dag. Noglevinterflokke viser fortsat tilbagegang eller uddørselv om det er et forvaltningsformål at opretholdebestandens nuværende geografiske udbredelse.Knap 60% af bestanden overvintrer på de tovigtigste overvintringsområder, Wexford Slobs idet sydøstlige Irland og Islay i det sydvestligeSkotland. Størstedelen af fuglene fra den nordligedel af yngleområdet overvintrer i Irland og trækkervia Vestisland, mens skotsk-overvintrende fugleviser tendenser til at yngle i de sydlige regioner afVestgrønland og bruge Sydisland under trækket.

Oprindeligt har den grønlandske blisgås udnyt-tet naturlige vådområdehabitater hvor de igen-nem årscyklus fouragerede på stænglerne af smal-bladet kæruld Eriophorum angustifolium. Før denmenneskelige påvirkning af deres vinterhabitaterbegrænsedes bestandens størrelse af udbredelsenaf uspolerede moser. Udnyttelsen af den speciellefødekilde i en begrænset habitat har sandsynligvisværet årsag til udvikling af stedtrofasthed ogforlænget forældre-afkom forhold som er karak-teristik for underarten.

I den anden halvdel af det 20. århundrede har degrønlandske blisgæs skiftet fra naturlige vådom-råder til kulturgræsenge. Især på Islay er der op-stået konflikt med landbrugsinteresser fordi gæs-sene forårsager markskader. På trods af ændrin-gen i habitatvalg er underarten forblevet megettraditionsbundet i valg af overvintringspladseridet nye fødevaner generelt er bundet til de tra-ditionelle overnatningspladser, og gæssene spre-der sig ikke til nye områder.

Formålet med denne afhandling at identificerefaktorer som potentielt begrænser bestandensstørrelse og regulerer raten i dens udvikling, ogdermed understøtte den mest effektive beskyt-telse og forvaltning af underarten i forhold til in-ternationale aftaler om forvaltning af fuglebestan-de og deres levesteder. I kraft af at gæssene ersociale, floklevende fugle, er det specielt interes-sant at belyse hvordan individuel adfærd påvir-ker overlevelse og reproduktion på individ- ogbestandsniveau.

Denne afhandling belyser årscyklus hos dengrønlandske blisgås med fokus på perioder medsærlige nærings- og energibehov (bl.a. træk, repro-duktion og svingsfjerfældning) og måder hvorpåindivider balancer deres korttids- og langtidsbud-getter. Kropsvægt og en visuel vurdering af fedt-lag er anvendt som mål for kropskondition.

Grønlandske blisgæs opretholder deres krops-vægt igennem vinteren, men viste stigende vægtfra midt af december indtil afrejse til Island imidten i april. Under antagelse af at 80-90% afdenne opbygning af depoter består af fedt, hargæssene rigeligt med brændstof til at gennemføreforårstrækket til Island alene på depoterne. Ho-vedparten af depoterne er brugt op ved ankomst-en til Island hvor de opholder sig i ca. 15 dage førtrækket videre til Grønland. I Island forøger dederes kropsvægt med 25-30 gram pr. dag.Sammenlagt er dette en smule mindre end forperioden december-april, men er akkumuleretover en meget kortere periode. De fleste gæsopnår disse højere rater af kropsvægtforøgelseved at søge føde på kulturgræsarealer som an-vendes til høslæt, suppleret med fødesøgning inaturlige vådområder. De tre mest udnyttedegræsarter udviser forskelle i profitabilitet i formaf forskelle i bladtætheder, vækstrater og næ-ringskvalitet. Disse faktorer påvirker gæssenesfødeindtagsrater og dermed tilvæksten i krops-vægt. Hos grønlandsk blisgås er adfærdsmæssigdominans er en vigtig faktor som sikrer adgangtil de bedste fødekilder. Fordi individuelle gæsviser forskellige niveauer af fødespecialiseringpå de tre græsarter kan tæthedseffekter og densocialt betingede dominans af adgang til fø-dekilderne påvirke indtagsraterne under ophol-det i Island, hvilket i sidste ende kan få fitness-konsekvenser.

Kropsvægten ved ankomst i Vestgrønland viserat gæssene taber mere vægt ved at flyve fra Is-land til Vestgrønland end på den samme distancefra Irland til Island. Forskellen svarer til denestimerede ekstra omkostning der er forbundetved at flyve over den grønlandske indlandsis. Ef-ter ankomst fouragerer gæssene intensivt i 10-14dage for at ombygge energi- og næringsreservertil æglægning. Vægtforøgelsen sker med sammehøje rate som i Island. Hunnen, som beskyttes afen agtpågivende mage, søger føde på energirigeunderjordiske planteorganer.

Dansk resumé

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Redestederne ligger i nærheden af moser medsmalbladet kæruld. Redetætheden er lav, ogredehabitaten forekommer ubegrænset. Derforforekommer det usandsynligt, at ynglehabitatenbegrænser den ynglende bestand. Derimod er dentilgængelige fourageringshabitat forud foræglægning i det centrale Vestgrønland begrænsetog kan påvirke gæssenes tilvækst af energi- ognæringsreserver. Stigende tætheder af gæs, somudnytter de begrænsede føderessourcer, kanpotentielt begrænse antallet af hunner, som kanopnå tilstrækkelig kropskondition til at gennem-føre reproduktionen med succes. Fugle, som yng-ler i Nordvestgrønland, gør ophold i det centraleVestgrønland på vejen til deres ynglepladser ogoplever konkurrence med lokale ynglefugle. Mo-deller for klimaforandring forudsiger, at der vilske en afkøling af forårs- og sommertemperatu-rerne i Nordvestgrønland, mens der vil ske enopvarmning af det centrale Vestgrønland. Såledeskan det forudsiges, at de nordlige ynglefugle vilmøde endnu flere gæs på vejen nordpå og dårli-gere klimatiske forhold på deres ynglepladser.

På trods af stigningen i bestandsstørrelsen, somer sket siden jagtfredningen i 1982, har det totaleantal af succesfulde ynglepar, der returnerer medafkom til de to vigtigste overvintringsområder,været stabilt. Det antyder, at en ressource - mestsandsynligt på ynglepladserne - nu begrænserrekrutteringen Blandt mærkede fugle med kendtalder er sandsynligheden for at overleve frem tilsuccesrig reproduktion faldet fra 15% hos ungerklækket i 1983 til 3% blandt unger klækket i 1992.Den gennemsnitlige alder ved ynglestart steg fraca. 3 år før 1988 til ca. 5 år i efterfølgende kohorter.Andelen af yngledygtige fugle, som returneredemed unger til overvintringsområdet, er faldendeved både Wexford og på Islay, men hurtigst vedførstnævnte, hvilket nu forårsager et fald i detsamlede antal, som overvintrer der. Muligvispåvirker afkølingen af klimaet i Nordvestgrøn-land og den øgede tæthed af fugle længere modsyd allerede nu Wexford-fuglene negativt, mensIslay-fuglene drager fordel af forbedrede klima-tiske forhold i det centrale Vestgrønland.

Grønlandske Blisgæs fælder deres svingfjer udenændring af kropsvægt, hvilket antyder at de kanopretholde deres nærings- og energibudgetter påexogene ressourcer. På grund af prædationsrisikofra Polarræv er gæssene tvunget til at opholde

sig i nærheden af vand, hvortil de kan flygte.Deres habitat er således af begrænset udbredelse.Canadagæs, som er under indvandring i Vest-grønland udnytter i stigende grad samme fæld-ningshabitat og er adfærdsmæssigt dominante iforhold til grønlandsk Blisgås. Der sker i disse åren dramatisk stigning i antallet af Canadagæs(som overvintrer i Nordamerika), hvilket sand-synligvis vil medføre en forøget konkurrencemellem de to arter.

Stigningen i bestandsstørrelse siden jagtfrednin-gen ved Wexford kan forklares ud fra en konstantårlig returneringsrate siden 1960erne. Det relativtstabile antal før 1982 synes at have væretopretholdt ved en balance mellem jagtdødelighedog ynglesucces. Umiddelbart efter jagtfredningen(dvs. efter bortfaldet af en tilsyneladende additivjagtdødelighed) steg antallet med en rate, som varreguleret ud fra ynglepotentialet, som overstegdødeligheden.

Siden begyndelsen af 1990erne er antallet afovervintrende fugle ved Wexford faldet som følgeaf faldende fekunditet og et katastrofalt tab afjuvenile fugle og deres forældre i et enkelt år.Reduceret fekunditet ser således ud til nutildagsat begrænse antallet af Wexford-fugle. Eftersomfekunditeten også er faldende på Islay og nogleandre overvintringspladser, ser det ud til at væreet generelt fænomen i bestanden i disse år. På Is-lay har reduktionen i fekunditet endnu ikkeforhindret den lineære fremgang i antal, som harfundet sted siden jagtfredningen.

Det ser således ud til, at før 1980erne varbestanden begrænset af jagtdødelighed. Efterjagtfredningen er bestandsstørrelsen steget til etnyt ligevægtsniveau, hvor reproduktionen erbegrænsende. Med de forudsagte klimaforan-dringer, stigningen i tætheden af gæs og Cana-dagæssenes kolonisering af yngleområderne, erdet sandsynligt at miljøforholdene, som vil på-virke bestanden af Grønlandsk Blisgås i fremti-den, vil forandres.

Afhandlingen afsluttets med, at resultaterne af 30års overvågning evalueres i lyset af de forhold,som kan tænkes at påvirke bestandens status ifremtiden. Der gives anbefalinger til forskning,som kan bidrage til en bedre forståelse af debagvedliggende processer.

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1.1 Why Greenland White-frontedGeese?

At the time when we first became interested inGreenland White-fronted Geese, it looked as ifthis race of the circumpolar White-fronted Goosewas in trouble. It was one of the few wildfowlspecies wintering in Britain and Ireland thatlacked adequate annual census data to determinethe trends in its population size. Such informa-tion as existed at that time strongly suggesteddeclines and extinctions at wintering resortsthroughout its range, especially in Ireland. Likemany migratory waterbirds at the time, it washunted throughout its entire range. Many featuresof this little population made it attractive to study:its breeding grounds in west Greenland werehardly known to Europeans, although first de-tails of its breeding biology had been describedas long ago as 1950. It was known that some birdsat least staged in Iceland, but very little wasknown about what the geese did there or the bio-logical significance of stopover staging there dur-ing migration to and from the breeding grounds.Finally, it was believed that the entire world popu-lation wintered in Ireland and western Britain,along the Celtic fringe of the European landmass.Here, its use of boglands and low intensity agri-cultural land in areas with some of the lowesthuman population densities on those crowdedislands meant that its precise distribution andabundance remained poorly known. Little won-der, therefore, that this race of geese attracted theattention of a dedicated band of students, all na-ively intent on discovering 'the secret' of its de-cline. The population had all the ingredients foran exciting investigation – a declining populationof birds using remote (and naturally beautiful!)landscapes in a relatively restricted part of theglobe! How could anyone not be intrigued by theprospect?

1.2 How much more do we know after aperiod of study?

Twenty years on, we know a great deal more, butwe are still very far from an adequate understand-ing of the ecology of the Greenland White-frontedGoose. We are now more confident that the popu-lation breeds exclusively in west Greenland

(MS23, MS24), stages on spring and autumn mi-gration in southern and western Iceland (MS4,MS15, MS16, MS18, MS19, MS25, MS26, MS27)and winters at some 70 regular winter haunts inwestern Britain and Ireland (MS14, Figure 1.1). Ithas proved possible, through international co-operation, to co-ordinate an annual census of thepopulation on the wintering grounds and to sam-ple age ratios in order to assess changes in pro-ductivity and monitor crude changes in survival.Satellite transmitter devices have been deployedon a sample of birds captured in Ireland to fol-low the precise timing, staging areas and routestaken by geese on migration to and from thebreeding and wintering grounds (MS20). Weknow a great deal more about the breeding biol-ogy and summer ecology of the populationthanks to summer expeditions to the breedinggrounds in 1979 and 1984 (Fox & Stroud 1981a,MS1, MS2, MS3, MS5, MS24). Based on continu-ing individual marking programmes, we nowhave long term monitoring of annual survival rateestimates (MS6, MS10), individual behaviour

1 Introduction

Figure 1.1. Current wintering distribution of GreenlandWhite-fronted Geese in Ireland and Britain (from Foxet al. 1999). Although dating from 1993/94, the distri-bution has not changed (in terms of the flock size in-tervals shown on the map) in the interim. Open sym-bols indicate regular wintering sites currently aban-doned (map generated using DMAP).

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(MS7, MS8, MS9, MS11), breeding success (MS8)and plumage characteristics (MS21). On the ba-sis of conservation concern for the population andthe availability of new data, a flyway conserva-tion plan was drafted for the population (Stroud1992), and more recently it was possible to un-dertake a Population Viability Analysis for thatelement of the population that winters in Britain(Pettifor et al. 1999).

Based upon the annual census information, theimportant conservation conclusion from all thisresearch and monitoring activity is that from apopulation size thought to have fallen as low as14,000 individuals in the late 1970s, the popula-tion now numbers some 33,000-35,000 birds (Fig-ure 1.2). Today, after a period of recovery underprotective legislation, the rate of increase in num-bers seems for the meantime to be slowing.

1.3 Why this synthesis now?

It could be argued that the job is now done. In-deed, the original imperative for this work (theobjective of restoring favourable conservation sta-tus to the population) has largely been achievedwithout seriously enhancing agricultural conflicton the wintering grounds. Surely this is a goodtime to stop? The following compilation demon-strates why the answer to this question is an em-phatic no! White-fronted Geese can live in thewild for 17 years (Cramp & Simmons 1977); hence,we have reached the point in time when the firstgeneration of marked individuals is likely alldead. Only now are we able to start to make ten-

tative statements about patterns of recruitmentand survival of cohorts of geese hatched in the1980s. Only through the sustained maintenanceof a marked sample of known age birds in a popu-lation such as the Greenland White-fronted Gooseis it possible to understand the subtle changes intheir long-term population dynamics. This is theproblem that faces biologists charged with an-swering short-term questions relating to long-lived individuals. For this reason alone, it is im-portant to step back and ask the question, howeffective has the study of marked individuals inthis population been in supplying answers tomanagement questions regarding it’s long termconservation management?

Population processes are influenced at a range ofspatial scales, and the interaction of phenomenathat affect populations at these different levelsshape overall population change (Wiens 1989,Levin 1992). We are fortunate, in the case of theGreenland White-fronted Goose, that it remainsfeasible to assess annual population size and re-productive output for a group of individuals thatsummer over a latitudinal range of 13º (some 1,700km north to south). Unusually, nowhere through-out this range does the breadth of their distribu-tion exceed 180 km, the maximum breadth of thewest Greenland landmass. Since the sub-speciesbreeds typically at low density, there is ampleopportunity for differences in local ecological,physical and meteorological conditions to affectlocal population processes through this long butvery narrow range. There are good grounds forbelieving that there is some segregation of birdsof different breeding areas on the winteringgrounds, so the scene is set for some interestingcomparisons of the behaviour of birds of differ-ent nesting provenance. Climate change modelspredict a general cooling of conditions in westGreenland, especially in the northern part of thebreeding range of the Greenland White-frontedGoose (Zöckler & Lysenko 2000). The same mod-els suggest that the summer temperatures of cen-tral west Greenland may increase slightly in theshort term, such that different changes in the cli-mate may simultaneously affect different ele-ments of the population. Since weather plays afundamental macro-role in the breeding successof many arctic migratory bird species (Ganter &Boyd 2000), there is an unique opportunity to fol-low a macro-experiment in the effects of climatechange on a whole population. Some of the base-line information offered in the following chap-ters seem to reflect the first effects of such change.

0

5000

10000

15000

20000

25000

30000

35000

40000

1950 1960 1970 1980 1990 2000

Tot

al p

opul

atio

n co

unt

Figure 1.2. Total annual estimated population size ofGreenland White-fronted Geese counted during co-ordinated count coverage on the wintering grounds(from Fox et al. 1999). Counts from the 1950s and late1970s are upper and lower estimates from Ruttledge& Ogilvie (1979).

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The Greenland White-fronted Goose is also ex-periencing inter-specific competition, as expand-ing numbers of Canada Geese Branta canadensisfrom North America colonise west Greenland,locally displacing the endemic Whitefronts. Wing-moult has been rarely studied as a critical elementin the life cycle of the Anatidae, yet it is preciselyat this period that competitive interactions be-tween the two goose species are most apparent(Jarrett 1999, Kristiansen 2001). The ecologicalconditions for breeding White-fronted Geese inwest Greenland are therefore most unlikely toremain as they are now, and the existing baselineinformation will prove invaluable for assessing,and making predictions about, future populationchange.

Having restored the population to more favour-able conservation status of greater numbers andmore stable population trends, the future chal-lenge is to maintain this status in the face ofgreater change and provide solutions to poten-tial conflict. There is a need to integrate the localscale with processes at the macro-scale, to assesslocal effects and build these into an understand-ing of overall population change. In particular,since we have evidence that there is some win-ter/summer segregation, what will be the effectsof changes in the summering areas on the winterdistribution and abundance of the population? Toanswer these questions is the challenge for theimmediate future. This will require the use of thematerial presented here to develop a forwardstrategy for research on this well-described popu-lation. Hopefully, such a synthesis would offer auseful model for understanding the effects ofcomplex changes on other migratory bird popu-lations.

Although they are not a major pest to agriculture,there is, nevertheless, local conflict between thesegeese and farming interests in a few winteringareas, notably in Scotland. Patterns of land-userarely stand still, and the changes brought aboutin rural land use on the wintering areas in thelast few decades have required that the geeseadapt to major modifications of the habitats theyhave exploited over recent periods and over alonger time span.

Climate change is also likely to be manifest onthe staging and wintering areas. Compared with20 years ago, we now understand a great dealmore about the biology and ecology of the popu-lation that can assist in developing adequate con-

servation management planning for this singu-lar race of geese.

In this way, we can offer solutions to some of thepotential conflicts, and provide informed judge-ments where predictions would have been im-possible a few years ago. More importantly, wecan use our knowledge and understanding of thispopulation to make more general inferences aboutother species and populations. As our under-standing of the energetics of migration is continu-ally improved, we can better understand the bio-logical importance of stopover and wintering sitesused by these migratory birds and the importanceof food quality and quantity, as well as the effectsof disturbance, to the overall fitness of individu-als. As we understand more about how the be-haviour of individuals contributes to their repro-ductive output and longevity, so we can makemore informed predictions about how humanactivities affect these individuals and scale up tothe potential impacts on the population as awhole.

The responses of individual organisms are not allthe same, especially in highly social animals suchas Greenland White-fronted Geese, where domi-nance hierarchies are well established and ex-tended familial relationships shape the individualresponses. We need to understand how changeaffects foraging and reproductive decisions madeby individuals, and to translate these local-scaleresponses through to the impacts at the popula-tion level. Such a process is epitomised by therecent development of individual-based behav-iour models of the annual cycle of migratorygoose populations (Pettifor et al. 2000). Such mod-els require detailed information about critical el-ements of the annual cycle of the birds, often inwidely differing and remote geographical areasat different times of the year. So how do we setabout identifying the critical elements and meas-uring their effects? Greenland White-fronts arelong distance migrants, flying perhaps 6000 kmin the course of their annual migrations alone, sothe factors affecting their reproduction and sur-vival (and ultimately their population size) maybe acting in many different ways in different partsof the globe.

1.4 The flyway concept

By definition, migratory waterbirds have evolvedlife history strategies that enable the exploitation

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of a series of habitats separated in space and time.Their mobility offers these organisms the abilityto exploit different habitats for different purposes.Alerstam & Högstedt (1982) were the first to sug-gest that, to survive between reproductive events,birds were exploiting what they termed 'survivalhabitats' which, for physical or practical reasons(e.g. predation risk), were not suitable for breed-ing. Equally, 'breeding habitats' (e.g. in arctic ar-eas experiencing extreme weather conditions)were not necessarily available to bird populationsbetween reproduction events. These authors sug-gested that the relative extent of these two habi-tats were important factors in determining repro-ductive and migratory tactics in different birdspecies. From an evolutionary standpoint, it istherefore important to recognise the role that dif-ferent habitats have played in shaping the life-history tactics of birds.

In a world increasingly modified by the activitiesof humans, the availability of both breeding andsurvival habitats to migratory birds has changed.In some cases, these changes have had a funda-mental effect on their distribution and abundance.Loss of wetland habitat has reduced the extent of'survival habitat' for many species. In contrast,the intensification of agriculture in the 20th Cen-tury has greatly increased the quantity and qual-ity of available forage in Western Europe forherbivorous waterfowl. The improved quality ofgrasslands (through enhanced crude protein con-tent, increased digestibility and extended grow-ing seasons) has undoubtedly increased the car-rying capacity of farmed land for avian grazingherbivores (van Eerden et al. 1996). If we are tounderstand the effects of anthropogenic changeson populations of migratory birds, we need toidentify the critical factors that affect their sur-vival and reproductive success and to establishat which points in the life cycle they operate. Itseems logical therefore to divide the annual cy-cle into a series of discrete events, to help iden-tify the specific bottlenecks faced by a waterbirdpopulation. In this way, it may be possible to iden-tify factors that either limit the size of that popu-lation (i.e. determine some upper level on thenumber of individuals that can be supported bya specific habitat at a given time) or that regulatethe rate of change in the population. The seasonalcomponents may have consequences for survival,reproduction or both and therefore represent criti-cal periods worth intensive investigation to iden-tify causal links between environmental factorsand population events. This conceptualisation of

the annual life cycle as a series of seasonal com-ponents which highlight the bottlenecks faced bywaterfowl populations was developed as the so-called 'Flyway Concept' by the Department ofCoastal Zone Ecology, pioneered by HenningNoer and Jesper Madsen. The original aim wasto integrate results from individual performance-based studies into a better understanding of howpopulations function, based on the variation inbehaviour of studied individuals, a mechanismnow well established in contemporary ecology(e.g. Sutherland 1995). This involved making de-tailed studies of individual habitat preference andfeeding behaviour and relating these to specificfecundity and survival measures of the same in-dividuals in order to understand which factorsregulate and limit populations.

Such an approach offers a useful template for usein identifying those processes in time and spacethat historically have affected the demographyof the Greenland White-fronted Goose popula-tion over the period for which we have some in-formation, and those that are doing so now. Inthis way, the life cycle can be broken down intothe critical elements, such as spring fattening,migration, breeding, wing-moult, autumn migra-tion and over-winter survival (e.g. Ens et al. 1994).Given that geese are generally long-lived, it isreasonable to expect that relatively small changesin annual adult survival are likely to have a ma-jor impact on their population size (e.g. Schmutzet al. 1997, Tombre et al. 1997). On the other hand,the relatively poor reproductive success offlavirostris, compared with that of other pan-arc-tic Anser albifrons populations, means that recov-ery of the population is slow because of low re-cruitment. The key questions are: what deter-mines natural annual survival? What effect doeshunting have on the population? Why is femalerecruitment into breeding age classes so low?These questions involve the role of spring stag-ing and the accumulation of stores for migrationand ultimately for investment in reproduction.What roles do the unusual extended family rela-tionships of flavirostris and individual experienceplay in limiting the proportion of geese of poten-tially breeding age that return from the breedingareas with young? The challenge has been to de-termine the role of body condition in individualdecision-making concerning migratory tactics,reproduction and survival. For this reason, em-phasis is placed here upon changes in body massand field-derived indices of fat deposits through-out the annual cycle in individuals, as proxies for

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more direct measures of 'body condition' in de-termining factors affecting individual perform-ance.

1.5 The flyway concept as related toGreenland White-fronted Geese andthe format of this thesis

The study of the Greenland White-fronted Goosehas never been a full time project for any of thecharacters involved. In Ireland, the National Parks& Wildlife Service has made a substantial annualcommitment to research and survey of GreenlandWhite-fronted Geese since the 1960s, when countsand age ratio assessments were made at Wexford.In more recent years, the regular marking of asample of individuals captured at Wexford andsubstantial effort invested in the resighting ofthese individuals has generated an impressivedatabase of knowledge to support the interna-tional research and survey effort. However, else-where, the work has been carried out on an adhoc basis, gathering data for differing purposesat different stages of the life cycle. The result issomething of a ragbag of information, not alwayswell inter-linked, and certainly never based upona single research plan with well-defined targetsand objectives. The available information is there-fore scattered, and one purpose of this thesis is todraw together the disparate strands in order todetermine what information is available and iden-tify the gaps in the existing knowledge.

Much of the reference material relating to Green-land White-fronted Geese has been gathered in arecent review and need not be repeated here(MS24). This forms the background to the thesis,in the sense that many of the results of studiesare summarised there. Chapter 1 establishes thesetting for the thesis. There follows a review oftaxonomic relationships and the recent history ofthe Greenland White-fronted Goose that attemptsto conclude something about the potential limitsto this population (chapter 2). The following chap-ters explore the elements of the life cycle wherecritical factors may operate with respect to fecun-dity or survival. Outside the breeding areas, thereare four periods of the annual life cycle whenGreenland White-fronted Geese must accumulatestores in anticipation of long migratory flights.The population stops off in Iceland in spring andautumn en route to and from Greenland. The geesemust accumulate energy stores enough to travelto and from Iceland and Greenland. Since spring

acquisition of stores in anticipation of the springflight to Iceland, and thence onward to Green-land will also have consequences for reproduc-tion, these two events in the annual life cycle haveattracted considerable interest, and have separatechapters to themselves (chapters 3 and 4).

On arrival in west Greenland after traversing theGreenland Ice Cap, the geese must again replen-ish depleted stores in preparation for the repro-ductive period. Geese were once thought to belargely capital breeders, investing stored nutri-ents in clutches and their incubation, althoughthis view is increasingly challenged (see reviewin Meijer & Drent 1999). In the case of the White-fronted Goose, it is now well demonstrated thatfemales indulge in extended periods of pre-nest-ing feeding when birds can add substantially totheir store of nutrients in readiness for egg-lay-ing and incubation (chapter 5). For a populationin which the reproductive success is well belowthe average for other populations of the samespecies, it is important to explore factors that maylimit recruitment and reproductive output (chap-ter 6). The period of flight feather moult repre-sents a potentially critical period in annual cycle,since birds become flightless for several weeks,making them more vulnerable to predation andthe depletion of local food resources until theyregain the power of flight. The duration of moultand the period of pre-migration accumulation ofstores in autumn are key elements in the annualcycle of the population (chapter 7).

The return flight from Greenland, again stoppingoff in Iceland, has been little studied, althoughthere remains the potential for occasional massmortality associated with this migration episode(as well demonstrated for other goose popula-tions, e.g. Owen & Black 1989, Boyd & Sigfussonin press). In comparison with high arctic forms,late summer and autumn are periods of plentyfor Greenland Whitefronts, when food in Green-land and Iceland is not especially limiting andthe weather is rarely sufficiently severe to causebetween year variation in adult annual survival.That said, there remains an autumn hunt of thispopulation, involving some 2,900-3,200 birds shotevery year in Iceland. This period remains a pri-ority for future research.

Having reached the overwintering habitat, it isimportant that this habitat is sufficient in quan-tity and quality to ensure survival. There wasconsiderable evidence that in the 1950s, habitat

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loss caused displacement of geese and over-har-vesting was responsible for the decline in the to-tal numbers of Greenland White-fronted Geese.For this reason, it is important to consider howfactors operating all year round and variationbetween and changes within winter habitats may

affect annual survival and immigration/emigra-tion rates on the wintering grounds (chapter 8).Finally, a concluding section draws together thedisparate strands of the thesis and offers somesuggestions for the direction of future research(chapter 9).

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2.1 Current taxonomic status

The Greater White-fronted Goose Anser albifronsis one of the most widely distributed large wa-terfowl species in the arctic (Ploeger 1968, Ely &Dzubin 1994). Four forms are currently recognisedas sub-species around the arctic region (see Fig-ure 2.1 and discussion below).

Coburn (1902) was the first to suggest that theWhite-fronted Geese in western Ireland more re-sembled those that wintered in North Americathan those in Europe. Nevertheless, it was as re-cently as 1947 that Christopher Dalgety and Pe-ter Scott first described the White-fronted Geesewintering in Ireland, Scotland and Wales as a newrace distinct from the European White-frontedGoose Anser a. albifrons. The new subspecies theynamed the Greenland White-fronted Goose Anseralbifrons flavirostris (Dalgety & Scott 1948). This

form is one morphologically distinct group fromthe circumpolar distribution, which extends fromthe central Canadian arctic (west of Hudson Bay)through to Alaska, and from the far east of Rus-sia to the Kanin peninsula (Figure 2.1).

Although there remains considerable discussionabout the precise taxonomic relationships, mostauthorities agree that the breeding range of thenominate race extends from the Kanin peninsulato the Kolyma river in tundra Russia (Cramp &Simmons 1977, Mooij et al. 1999). To the east ofthis, it is replaced by frontalis in Russia, whichwinters in the eastern Palearctic. This sub-speciesalso breeds across North America and winters inMexico and along Gulf and Pacific coasts (Ely &Dzubin 1994). However, intensive studies fromthe Pacific flyway show that allopatric Alaskanbreeding groups maintain temporal separation onstaging and wintering areas which has probably

contributed to the evolutionof previously describedphenotypic differences be-tween these populations(Orthmeyer et al. 1995, Ely& Takekawa 1996). Theseauthors suggest that thesesub-populations, along withthe Tule White-frontedGoose (A. a. gambelli whichbreeds in Cook Inlet, Alaskain the taiga zone and win-ters in Oregon and Califor-nia), may represent part ofa 'Rassenkreis', a group ofsubspecies connected byclines. Such a situation ismaintained over timethrough limited but regulargenetic exchange betweenunits otherwise segregatedin time and space. Hence,the internal genetic uni-formity of the existing taxo-nomic units is unlikely to beas simple as the currentsub-species structure mightsuggest. Nevertheless, inthis respect, flavirostris re-mains amongst the mostgeographically isolated

2 Limits to population size in recent historical times

Figure 2.1. Breeding distribution of currently recognised White-fronted Goosesubspecies, flavirostris (Greenland), frontalis (Nearctic and Eastern Palearctic),gambelli (Alaska) and albifrons (Palearctic), based on Cramp & Simmons (1977)and Ely & Dzubin (1994).

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unit of all the forms, a feature that is likely to havemaintained a distinct genetic identity, at least inthe period since the last glaciation.

2.2 Evolutionary history

Johansen (1956) suggested that White-frontedGeese evolved from the closely related GreylagGeese Anser anser that is known from the Pliocenein central Europe (<7 million years before pres-ent), whereas the earliest White-fronted Goose re-mains are only of Pleistocene origin (<2.5 millionyears B.P.). This has since been confirmed by re-cent genetic evidence (Ruokonen et al. 2000). Thisis consistent with the general impression of sis-ter-species separations in avian groups during thePliocene, whereas the oscillating Pleistocene cli-matic conditions were more active in phylogeo-graphic separation within species (Avise & Walker1998).

It seems likely that towards the end of the Tertiaryperiod, when the arctic climate became substan-tially colder, White-fronts segregated from thelarger ancestral Greylag form, which would havebeen expected to remain further south in more tem-perate conditions. From this Old World origin, theWhite-fronted Goose was able to spread through-out the entire arctic, colonising the New Worldduring the Hoxnian Interglacial (note the Britishnomenclature for Quarternary periods is usedthroughout here for consistency: 400,000-367,000year B.P., Figure 2.1, Fox & Stroud 1981b). The sub-sequent Wolstonian glacial period (which contin-ued to 128,000 years B.P.) forced these forms southagain, probably resulting in the isolation of 'At-lantic' and 'Pacific' forms. During the last intergla-cial period (the Ipswichian 128,000-60,000 yearsB.P.), the latter spread widely from refugia in theBering Sea region in both directions, resulting inthe presence of frontalis in the eastern Palearctic.

Johansen (1956) suggested that, during the lastglacial (the Devensian 60,000-12,000 years B.P.),the nominate race survived in north Siberia ref-uges. The frontalis form persisted in the BeringianRefugium, recolonising North America during thesubsequent amelioration and he considered thatthe ancestral Atlantic form gave rise to flavirostris,which survived the last glaciation in the ice-freetundras of western Europe, especially the south-ern North Sea and Ireland.

Later, Ploeger (1968) offered four different possi-

ble origins for flavirostris. (1) He considered thatthere were morphological similarities betweenflavirostris and albifrons that pointed to a commonorigin, and that the present separation was theresult of the use of different refugia in the NorthSea area and Siberia respectively. (2) Alternatively,flavirostris detached from eastern AmericanWhite-fronted Geese after their spread acrossNorth American tundras in post-glacial times. (3)Another possibility is that flavirostris was the east-ern element of a pre-Devensian White-frontedGoose population that managed to survive ineastern North America. (4) Finally, he consideredflavirostris could represent an older populationdifferentiated from other forms at an earlier stage,which spread westwards from Eurasia before thelast glacial period.

Of the above, (1) seems the least likely now.Based on various length parameters, flavirostrisis more different to the nearest albifrons (nestingsome 3,500 km east in Kanin) than to any othercircumpolar A. albifrons forms (from tarsus, billand wing measurements from A. albifrons caughtthrough the range, C.R. Ely in litt.). Indeed, basedon measurements, flavirostris is most like albifronsfrom the Central Canadian arctic (which nestssome 1,500 km west) and the sub-arctic gambelliof Alaska (C.R. Ely in litt.). If similarity of mor-phological form can be relied upon in this re-spect, this suggests that the race is more likelyto have originated from easternmost elementsof White-fronted Goose populations in NorthAmerica. Furthermore, during the glacial maxi-mum of the last glacial period, ice extendeddown to the southern North Sea, joining ice capsthat covered Greenland, Iceland and Scandina-via. Despite lowered sea levels, there was nevera time when there were land bridges betweenGreenland and Iceland or between Iceland andNorth Sea tundra areas. Hence, if GreenlandWhite-fronted Geese had North Sea refugia, atsome stage since the height of last ice age, theancestral stock must have shifted their breedinggrounds to Iceland and thence from Iceland towest Greenland. The distances involved in thesedistributional leaps would have been almostexactly the same as the migratory journeys atthe present time. However, there remains con-siderable debate as to whether there were ice freeland areas in west Greenland and Iceland (seePloeger 1968, Denton & Hughes 1981, and Fig.12 in Piersma 1994), so it may well be that Green-land White-fronted Geese have been long sepa-rated from other stock.

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Despite the morphological similarities to supporta recent New World origin for flavirostris, there isno suggestion of regular wintering grounds forWhite-fronted Geese in the eastern United States,where flavirostris remains a rare vagrant (e.g.Hewitt 1948, Parkes 1960, Finch 1973). At thetimes of maximum extent of ice cover during re-cent glacial periods, there were never land bridgesbetween west Greenland and Canada (Andrews1982). It is also interesting to speculate how an-cestral Greenland White-fronted Geese originat-ing in North America came to have a Palearcticmigration system like that of the Old WorldWheatear Oenanthe oenanthe that also breeds inwest Greenland but migrates to Iceland to Europeand Africa in autumn.

All of the potential theories relating to origins offlavirostris suffer from weaknesses of one type oranother, and the available fossil and other evi-dence simply does not exist to support or refutethese ideas. The current distinct feeding ecologyand habitat use of flavirostris, if long established,would have restricted its distribution. The exploi-tation of wetlands of a particular maritime type,especially peatland formations, would have re-stricted the race geographically to its currentworld range on the mild western fringe of theEuropean landmass. The geographical, morpho-logical, behavioural and demographic character-istics of the sub-species suggest its long separa-tion from other presently existing races, but con-firmation will have to await appropriate geneticanalysis embracing all the different forms identi-fied within the current Anser albifrons. Collabora-tive analysis is currently well advanced to de-scribe the morphological variation in differentpopulation elements (Ely et al. in preparation).This will be the precursor to a major genetic analy-sis (based upon an existing and growing archiveof blood samples gathered from around the arc-tic) to establish more clearly the phylogeny of thisspecies and its various described sub-species.

2.3 Factors affecting the currentdistribution

The present wintering distribution of the Green-land White-fronted Goose is concentrated alongthe northern and western fringes of Britain andIreland (Fox et al. 1994a, MS14). This distinctivedistribution mirrors the climatic template for theformation of oceanic blanket bog. This habitatformed the traditional overwintering habitat for

the subspecies before Man substantially modifiedthe landscapes of Britain and Ireland (Ruttledge& Ogilvie 1979, Fox et al. 1994a).

The Greenland White-fronted Goose specialiseson feeding by up-rooting cyperacean species toconsume their nutritious lower stem storage or-gans. In particular, the common cotton grassEriophorum angustifolium was, or is still, eaten bythe geese in Scotland, Wales, Ireland, Iceland andGreenland (Ruttledge 1929, Cadman 1953, 1956,1957, Pollard & Walters-Davies 1968, Madsen &Fox 1981, MS2, MS4, Fox et al. 1990). This speciesof cotton grass is common throughout WesternEurope, but thrives well where high rainfall anda mild wet climate creates patterned blanket andraised mire systems. Oceanic mires characterisedby such complex surface topography have well-developed water- and Sphagnum moss-filled de-pressions. Although not necessarily the optimumconditions for the growth of E. angustifolium, suchwet peatland depressions facilitate the easy ex-traction of the lower stem parts of the plant fa-voured by the geese. In contrast, E. angustifoliumcan be vigorous and abundant in more mineralwetland soils, but in such situations, the below-ground plant parts are difficult or impossible toextract by geese.

On the same oligotrophic bogland habitats, theGreenland Whitefront also consumes the White-beaked Sedge Rhynchospora alba, which over-winters as small bulbils which are highly nutri-tious and much sought after by the geese (Cad-man 1953, 1956, 1957, Pollard & Walters-Davies1968).

The Greenland White-fronted Goose is also con-fined to an area of Britain and Ireland defined bythe mean January 3ºC isotherm (Belman 1981).The low probability of prolonged ground frostthroughout the winter period within this rangeis thought to be an important factor that permit-ted the geese to extract the subterranean stembases of Eriophorum and bulbils of Rhynchosporafrom the soft Sphagnum cuspidatum, S. auriculatumand S. recurvum lawns (MS24). This theory is sup-ported to some extent by the fact that at least 4flocks in Ireland and 1 in Wales became extinctafter the severe winter of 1962-63. In that winter,daily sub-zero temperatures occurred continu-ously in western Britain from 23 December 1962until 6 February 1963 (Beer 1964). In that period,Greenland White-fronted Geese were displacedwhen their bogland habitats were frozen, and

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birds were picked up dead or dying away fromtheir normal haunts (Ruttledge & Ogilvie 1979,Fox & Stroud 1985). Large numbers of albifronsalso died of starvation that year, but there was noevidence of range contraction for this population,which is less winter site-loyal and feeds more onagricultural grasslands (Beer & Boyd 1964).

Even where flush runnels and the pool and hum-mock topography are abundant as surface fea-tures, their extent (and therefore the extent of cot-ton grass and other favoured peatland food spe-cies) represents a tiny fraction of the entire bogbiotope. Furthermore, by definition, their distri-bution is highly patchy, so any herbivore exploit-ing such a resource would be expected to showappropriate behavioural and feeding ecologyadaptations. For example, because both Eriopho-rum angustifolium and Rhynchospora alba are onlylocally abundant, foraging could rarely take placein large flocks, since no one area could supportmore than 10-20 foraging individuals for pro-longed periods. The broken topography of blan-ket and raised mire systems makes approach bypotential terrestrial predators (such as Fox Vulpesvulpes) relatively simple. Hence, shared vigilancewould be expected to favour the cohesion of smallgroups defending feeding patches rather thanlone foraging individuals prepared to risk pre-dation as the costs of gaining access to interfer-ence-free foraging opportunities and maintainhigh intake rates. On the other hand, the locallyrestricted, patchy but rich food resource wouldhave precluded the development of large flockstypical of other subspecies of Anser albifrons ex-ploiting open grass swards.

For the reasons considered above, the subspecieswas probably always highly restricted in its win-tering distribution. Oceanic mires with conspicu-ous surface patterning reach their southern limitin Britain and Ireland (Lindsay 1995, Lindsay &Immirzi 1996), and those in Scandinavia to theeast and north are frozen in winter rendering thefood inaccessible to the geese. In recent centuries,the wintering range is unlikely to have been verydifferent from that today, and the habitat signa-ture that defines their distribution would havealways been highly limited in extent, even allow-ing for widespread loss of boglands as a result ofMan’s activities in the last 500 years.

Heavy exploitation by Whitefronts may locallyremove all Eriophorum shoots, and the plant maytake a year or more to recover to levels of biomass

prior to goose exploitation (Hupp et al. 2000,MS24). This also has consequences for the way inwhich a herbivore should exploit the feeding re-source, since exploitation of one feeding patch inyear t may render this area a poor foraging areain year t+1 and perhaps even in t+2. Hence someknowledge of the spatial arrangement of thispatchy feeding resource and the location of alter-native feeding sites (that can be used in succes-sive years) might also favour a social system thatinvolved learning by young members of a groupabout alternative feeding sites (linked perhaps bya common night-time roost site).

The geographical distribution of the GreenlandWhite-fronted Goose may always have beenhighly restricted, limited by a rich feeding re-source that sustained the geese throughout thewinter, the distribution of which was highlypatchy, both in time and space. This presumablyfavoured high site fidelity and the “cultural” ac-cumulation of knowledge as the most effectivemeans of exploiting the bogland biotopes. Thisin turn resulted in low densities of these special-ised herbivores concentrated in relatively smallpockets of habitat. If the Greenland White-frontedGoose was confined to bogland habitats in thisway, it seems likely that the population wouldalways have been extremely limited in its rangeand abundance by the nature of its habitat.

2.4 Changes in habitat and abundance inthe 20th Century

Given the waterlogged nature of their habitat, andthe inaccessibility of many of their winter haunts,the Greenland White-fronted Goose winteringhabitats were probably left largely untoucheduntil the mid 19th Century, with many peatlandareas unmodified well into the 20th Century. De-spite the need for fuel from peatlands, domesticturbaries were unlikely to have extracted peat byhand at a rate that would have threatened thegoose habitat. Indeed, there is evidence from atleast 5 different Welsh, Islay and west of Irelandwintering sites, that abandoned hand-cut peatdiggings perpetuated feeding habitat for Green-land White-fronted Geese, by creating the wetfloating Sphagnum lawns from which the foodplant Eriophorum can be most easily extracted (Fox& Stroud 1985). Furthermore, despite the pres-sure of human densities on the land that resultedin the creation of 'lazy beds' in the most extraor-dinary situations in the highlands and islands of

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Scotland, the wettest peat soils were so infertileand waterlogged as to offer a last refuge for wild-life at that time from a hungry human popula-tion. Greenland Whitefronts were described asnumerous and widespread throughout the bogsof Ireland (Ussher & Warren 1900), but extensivedrainage, started during 1845-1855, was thoughtto have made the first impact on goose feedinghabitat, resulting in many geese being forced toleave their traditional habitats (Ruttledge &Ogilvie 1979).

Seasonally flooded grassland (such as the callowsof the Shannon Valley floodplain in Ireland) wasprobably always of some importance as winter-ing habitat for Greenland White-fronted Geese(H.J. Wilson in litt.). During the 20th Century,whether because of drainage and destruction oftheir former natural habitats, or through theirdiscovery of the foraging opportunities offeredby low intensity agricultural grassland, Green-land White-fronted Geese increasingly resortedto rough pasture in Ireland and Scotland. Al-though the geese may still utilise boglands andpeat systems for night-time roosts, there are fewflocks that continue to feed exclusively on natu-ral habitats throughout the winter (Norriss &Wilson 1993, Fox et al. 1994a, MS14). The increas-ing use of semi-natural grasslands apparentlyaccelerated in the latter half of the 20th Century,when there was also an increase in the extent andgoose use of intensively managed farmland. Al-though habitat destruction has been cited as thecause of shifts in habitat use of this species (e.g.Ruttledge & Ogilvie 1979), Norriss & Wilson(1993) were strongly of the opinion that the move-ment from semi-natural grasslands to more in-tensively managed agricultural land coincidedwith beneficial changes, rather than losses of tra-ditional habitats. They observed that goose useof reseeded grasslands was typically opportun-istic within existing feeding areas, whilst longerestablished, poorer quality habitats were aban-doned. Hence, in terms of responses to new feed-ing opportunities provided by the dramatic ratesof changes in agriculture in the last 50-100 years,the Greenland White-fronted Goose may haveshown greater flexibility in adapting to newsources of food than might have been expected.

This adaptability was nowhere more dramaticthan in the vicinity of Wexford Harbour in SE Ire-land. At the beginning of the 20th Century, theWexford Slobs were embanked and claimed foragriculture from the intertidal waters of Wexford

Harbour. Whitefronts began using the newly cre-ated large fields of rough grassland of the area,so that by 1925, this was already the most impor-tant Irish wintering site as it remains to the present(Kennedy et al. 1954, MS14).

In Britain, the compilation of a historical pictureof the distribution and abundance of GreenlandWhite-fronted Geese in winter was complicatedby the occurrence of European White-frontedGeese A. a. albifrons from Russian breeding areas(which do not occur in Ireland). Since the sub-species was only defined in 1948, it is not possi-ble to determine the breeding origins of White-fronted Goose wintering groups with certaintybefore that time. The White-fronted Goose wasto be found in the late 19th and early 20th Centuryin nearly all the haunts where flavirostris occurstoday (Berry 1939, Ruttledge & Ogilvie 1979). Thisincluded Islay, identified as the principal hauntfor the species as long ago as 1892, supporting“large flocks”, as well as Tiree, Coll and Jura(Harvie-Browne & Buckley 1892). The species hascertainly been long established in Caithness andOrkney (Harvie-Browne & Buckley 1887, 1891).The only notable change appeared to be on theOuter Hebrides, where the species was consid-ered rare until the late 1800s when it was reportedin markedly increasing numbers (Harvie-Browne& Buckley 1888, Berry 1939). However, large num-bers have probably always passed over the West-ern Isles on passage in spring and autumn, whenlarge numbers may temporarily also land, so theirfluctuating fortunes may have more to do withthe interpretation of such patterns than any dra-matic change in over-wintering abundance. Win-tering flocks of White-fronted Geese were alsoknown in the 19th and early 20th Centuries fromNorth Wales (Fox & Stroud 1985), Lancashire andWestmoreland. All were associated with inun-dated wetlands or former peatland areas. It ishighly probable, based on their reported habitatuse, that most of these would have been Green-land birds.

As in Ireland, the use of traditional bogland habi-tats for daytime feeding has become increasinglyrare amongst British-wintering flocks, as geeseforage increasingly on grasslands. The major con-centrations on Islay and Kintyre increasingly ex-ploit intensively managed agricultural grass-lands, even though they supplement their diet byf0eeding on bogland roosts at night (MS24). Evenin Caithness, where geese still fed by day on theFlow Country patterned mire peatlands until the

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1970s, all are now confined by day to agriculturalhabitats (MS24).

In 1960, Major Robin Ruttledge became aware thatnumbers of Greenland White-fronted Geese hadbeen decreasing in Ireland over at least a decadeand he issued a circular to contacts in an attemptto determine if this was widely the case. The re-sults of his survey and extensive correspondenceconfirmed his suspicions that numbers had de-clined throughout the range and some formerhaunts were deserted (Ruttledge 1973). By con-trast, at the same time, apart from the desertionof one important Welsh site, Cors Caron (not con-nected with habitat change, Fox & Stroud 1985),rather little change was taking place amongst theknown flocks residing in Britain. Major Ruttledgeand Malcolm Ogilvie began to compile the his-torical information available relating to winter-ing Greenland White-fronted Geese and theypublished their findings (Ruttledge & Ogilvie1979).

The historical evidence for changes in the size ofthe Greenland White-fronted Goose populationis relatively limited, since prior to the 1940s, in-formation is scant and anecdotal. Although theWildfowl Trust had pioneered the developmentof count networks and research programmes intomost wintering goose populations in Britain dur-ing the 1950s, the Greenland Whitefront, with itsremote wintering resorts and highly dispersednature was far less known. Hugh Boyd estab-lished regular counts on Islay in the 1960s andsampled the proportion of young birds in eachwinter there. Malcolm Ogilvie continued this an-nual count during his counts of Islay-winteringBarnacle Geese Branta leucopsis from the Green-land population. In the mid-1950s, Boyd (1958)analysed the ringing/recovery data generated bythe capture programme initiated in Greenland byFinn Salomonsen at the Zoological Museum inCopenhagen. At Wexford, Oscar Merne estab-lished regular counts of the Whitefronts in the late1960s, incorporating an assessment of the propor-tions of young in the flocks.

Information before these efforts was very scanty.Berry (1939) and Baxter & Rintoul (1953) were thefirst to attempt a summary of the status of theWhite-fronted Goose based on available informa-tion, but this did not enable an assessment of over-all abundance. Atkinson-Willes (1963) suggestedBritish wintering numbers during 1946-1961 tobe 2,500-4,500 and Ruttledge & Hall Watt (1958)

estimated 8,850-11,200 in Ireland during 1946-1956. However, Ruttledge & Ogilvie (1979) re-viewing additional information available follow-ing that time suggested totals of 4,800-5,800 inBritain and 12,700-17,300 in Ireland in the 1950s.They carried out the first full collation of avail-able information and concluded that the globalpopulation had declined from 17,500-23,000 atthat time to 14,300-16,600 in the late 1970s, whichthey attributed largely to loss of habitat (especiallyloss of bogland habitats in Ireland), shooting anddisturbance. They considered that the Irish win-tering numbers had declined by 50% from the1950s to the 1970s despite stable numbers at themost important site Wexford Slobs. This includedthe desertion of at least 29 sites and declines at afurther 33. During the same period, the Britishpopulation had actually increased overall byc.13%, especially in Scotland, although 2 flockextinctions of 100 (Morecambe Bay, England) and450 (Cors Caron, Wales) and 3 flock declines werenoted. The net loss of 7,000 geese from Irelandwas not, however, balanced by the gains in Scot-land (c. 2,000 birds, Ruttledge & Ogilvie 1979).

Thorough as the survey of Ruttledge & Ogilvie(1979) was, these authors missed a very smallnumber of flocks, especially in remote Scottishsites. Hence, subsequent survey has indicated amodest increase in the number of traditionalflocks over those that they reported.

The reasons for the extinctions and declines wereinevitably site specific, the majority of the changesat Irish sites being ascribed to afforestation, drain-age or (in some cases) complete removal of peat-lands as a source of fuel (Ruttledge & Ogilvie 1979).At some sites, the same authors also cited shoot-ing and hunting disturbance as contributory fac-tors. By the late 1970s, it had become clear thatthere was an urgent need for information relat-ing to the status and distribution of the subspe-cies on its wintering grounds in order to fullydetermine the conservation needs of the popula-tion (Owen 1978).

The decline of the wintering flock of GreenlandWhite-fronted Geese wintering on the Dyfi estu-ary in central Wales attracted the attention of agroup of students who started to undertake re-search and established the Greenland White-fronted Goose Study (GWGS) in the late 1970s.This group set up a regular count network at allknown sites in Britain. Its further aim was to studyand obtain further information about all aspects

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of this goose population. At the same time, thepioneering work of Major Ruttledge laid the ba-sis for the establishment of a network of countersin Ireland, co-ordinated by John Wilson and DaveNorriss of the Irish Forest and Wildlife Service(latterly the National Parks and Wildlife, Dúchas,The Heritage Service). The network comprisesmostly Conservation Rangers supplemented withBirdWatch Ireland volunteers and collates habi-tat, disturbance, production data as well as or-ganising the counts. These counts aimed to pro-vide an assessment of numbers at all known win-tering sites at least twice a year (generally month-ly throughout the season where possible) with ameasure of breeding success based on a sampleof the proportion of young birds of the year. Thissystem has now been operating annually since1982/83 and generates annual population esti-mates and assessment of breeding success (Foxet al. 1994a, MS14).

2.5 Changes in distribution andabundance since protection in 1982/83

Before 1981, the Greenland White-fronted Goosewas legal quarry throughout its entire range.There is little doubt that during 1950-1970, thepopulation was suffering damaging effects ofhabitat loss and modification on the populationas well as a considerable off-take that occurredthrough hunting. Birds were being captured andkilled on the breeding areas, shot legally in Ice-land in autumn, as well as poached illegally therein spring. Substantial numbers were shot on thewintering areas, particularly in Ireland (wherethis was one of the few wild goose species widelyavailable as a quarry species).

Following the first appraisal of the global distri-bution and abundance of the population in the1970s, conservation concern was expressed for theGreenland White-fronted Goose, particularly be-cause of the decline in numbers in Ireland duringthe 1950s-1970s (Owen 1978, Ruttledge & Ogilvie1979). As a relatively long-lived bird, the Green-land White-fronted Goose is sensitive to evensmall scale changes in annual adult survival.Limitation of the hunting kill was an obviousmanagement response to attempt to restore thepopulation to a more favourable conservation sta-tus. Hence, the conservation status of the subspe-cies was modified throughout its range, especiallythrough protection from hunting, and in latteryears, through site safeguard programmes (see

Stroud 1992 for full details of protection meas-ures). In summary, the population ceased to belegal quarry in Ireland and Scotland from 1982(although this moratorium was lifted at Wexfordin the winters of 1985/86 and 1989/90 under strictbag limitation) and in Northern Ireland in 1985.The species has been protected at its only remain-ing regular wintering site in Wales, the Dyfi Es-tuary, by a voluntary shooting ban in place since1972 (Fox & Stroud 1985). In Iceland, the speciesremains legal quarry in autumn where 2,900-3,200geese have been shot each year (Wildlife Man-agement Institute 1999). There has been no sig-nificant trend in the proportion of marked birdsrecovered in Iceland annually since 1984 (F15 =0.11, P = 0.74), suggesting a constant proportionhave been shot over this period (mean 3.8% ± 0.40SE marked birds shot and reported in Iceland perannum). Since 1985, the population remains le-gal quarry in Greenland only during 15 August –30 April, extending the protection in the nestingseason to spring migration as well. It is thoughtthat currently some 100-200 geese are shot thereannually (MS24).

Given the high site fidelity shown by the specieson the breeding, wintering and staging grounds(MS5, MS7, MS9, MS27), site safeguard is clearlyan important element in any nature conservationstrategy to maintain key areas and hence main-tain the existing size of the population (Stroud1992). Use of the Ramsar 1% criterion for site pro-tection has proved an effective mechanism to fo-cus conservation priorities on the larger concen-trations, but fails to protect the sites used by thesmaller more vulnerable flocks that show themost dramatic declines (MS14). Nevertheless, siteprotection in the UK (through EEC Birds Direc-tive SPAs, Ramsar Wetlands of International Im-portance, National Nature Reserves (NNRs) andSites of Special Scientific Interest (or in NorthernIreland - Areas of Special Scientific Interest (ASSIs)cover, in whole or in part, habitats used by geeseat 22 sites. The UK SPA network is anticipated tosupport at least 8,000 geese at 12 SPAs specifi-cally classified for Greenland Whitefronts (an es-timated 59% of the British total and 28% of theinternational population in the mid-1990s; Stroudet al. in prep.). The SPAs include a state-ownedNNR, Eilean na Muice Dubh/Duich Moss on Is-lay, the most important single roost site in the UK.This was acquired following the threat of com-mercial peat cutting in the 1980s (Stroud 1985;Nature Conservancy Council 1985; GreenlandWhite-fronted Goose Study 1986). Statutory pro-

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tection measures are supplemented by nature re-serves established by non-government organisa-tions, such as the Royal Society for the Protectionof Birds (five reserves - on Islay, Colonsay, Coll,Loch Ken and the Dyfi Estuary).

In the Republic of Ireland, site protection is nowfounded upon designation of internationally im-portant sites and Natural Heritage Areas (NHAs,formerly Areas of Scientific Interest ASIs). Fifteenactual or proposed SPAs and/or Ramsar sites, 31NHAs and 4 additional areas covered by man-agement agreements in Ireland protect areas usedby all but 5 of the regularly wintering GreenlandWhite-fronted Goose flocks. However, the extentof site-protection is less than the total area usedat some localities.

In Iceland, there is only one site with formal pro-tection used by Greenland White-fronted Geese,but the most important staging area, HvanneyriAgricultural College in the west of Iceland, iscurrently being negotiated as a potential reserve.The current voluntary ban on shooting at this onesite has made this the single most important stag-ing area in Iceland, with up to 1,600 geese stag-ing in spring and probably more in autumn.

In Greenland, the Home Rule Authority an-nounced the declaration of five major Ramsarwetlands of international importance in 1989,covering some 700,000 hectares of the goose sum-mering areas (see Jones 1993 and Fox et al. 1994afor full details). Based on aerial survey in 1992, itwas judged that the protected areas north ofKangerlussuaq (including Eqalummiut Nunaat),Naternaq, and three important areas on DiskoIsland: Aqajarua-Sullosuaq, Qinguata-Kuussuaqand Kuannersuit kuussuat together hold approxi-mately one fifth of the summering population.The very important wetlands of the SvartenhukPeninsula have also been considered for futuredesignation as a Ramsar site.

With the provision of such site safeguard meas-ures, the population has clearly seen a recent haltin the serious losses of habitat that it experiencedduring the 19th and 20th Centuries. Nevertheless,throughout the wintering areas, nature conserva-tion protection has concentrated upon protectionof the most important natural and semi-naturalhabitats, as well as safe roost sites that have beenused for many years. Rarely do site managementplans include specific measures to maintain andenhance habitat quality and quantity specifically

for the geese. Since Greenland White-frontedGeese have increasingly shifted to feeding onagricultural land on the wintering areas wherethe feeding habitat is not in anyway safeguarded,'wider countryside' conservation measures inthese agricultural areas may be appropriate tosupport site safeguard of roosts in some situa-tions. In these circumstances, especially in theRepublic of Ireland, local management agree-ments have been adopted to maintain local agri-cultural conditions suitable for geese. Only in rela-tive few situations in Ireland have land acquisi-tions by the state resulted in major reserves spe-cifically for White-fronted Geese. This is the caseat Wexford Slobs Wildfowl Reserve in SE Ireland,where 470 ha of farmland have been acquiredprimarily for feeding and protecting GreenlandWhite-fronted Geese during the winter and pro-viding increased public awareness through visi-tor observation and interpretation facilities (Wil-son 1996). There also remains considerable scopefor improving site safeguard measures in Iceland.

Following protection from hunting on the win-tering range in 1982/83, the population increasedfrom 16,500 in 1983 to 33,000 in 1999, althoughthe rate of increase has slowed in recent years.The population increased at the rate of 6.6% perannum until 1991/92, since when total numbershave varied between 30,000 and 35,000, depend-ent largely upon changes in breeding success. Themost dramatic increases were evident at the twomost important wintering resorts. At Wexford,peak winter counts increased from 6,300 in 1982/83 to 8,500 in 1999/2000 (after a maximum of11,000 was reached in 1988/89) and Islay from3,900 to 13,800 (after a peak of 15,400 in 1995/96see Figure 2.2). One feature that makes flavirostrisof special interest is that different winteringgroups show very different patterns of popula-tion change, despite the overall increase in num-bers. Wintering numbers on Islay have shown alinear increase under protection, whilst those atWexford have decreased in recent years after aninitial period of increase (Figure 2.2, MS14). Otherflocks have shown less dramatic increases; fromregular counts at eight wintering sites in yearsbefore and after protection, five sites showed notrend before protection and significant increasesafterwards, two stabilised after protection andone showed increasing trends before and afterprotection (MS14). Seven flocks became extinctduring 1982-1995, 35 showed no significant trendsand 20 showed increases (MS14). Despite all theconservation activity, therefore, some flocks con-

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tinue to decline in number or disappear, a proc-ess which is not matched by colonisation of newwintering sites, only one of which, in eastern Ire-land, seems to have become regular.

2.6 What of the future for the GreenlandWhite-fronted Goose?

The conservation of a relatively small populationof one race of an abundant circumpolar species isnot a high priority in its own right. Nevertheless,the Greenland White-fronted Goose became a“flagship” organism for the conservation ofpeatlands on its wintering grounds during the1980s, representing a top consumer organism offragile peatland systems under threat from for-estry, commercial peat exploitation and drainageat that time. Even in areas where they no longerfeed on peatlands, the geese exploit features ofan extreme oceanic low intensity pastoral systemthat supports a rich ecologically diverse commu-nity (Bignal et al. 1988, Bignal & McCracken 1996).Conservation actions to protect Greenland White-fronts in winter therefore safeguard a set of unu-sual and scarce habitats that also support otherbreeding and wintering species. The research andconservation effort invested in the populationover the years now provides a long time series ofannual numbers, distribution and breeding suc-cess amongst a discrete population of migratorywaterbirds. The marking programme, started inGreenland in 1979 and continued to the present(largely in Ireland where birds continue to be col-lared on a regular basis), provides a 20 year recordof individual life histories. In the fullness of time

(since these geese are long lived), these recordswill provide important additional insights onchanges in such critical parameters such as ageof first breeding, lifetime reproductive successand mortality. The very process of studying thispopulation has given the Greenland White-fronted Goose scientific interest which may offersome insights into population processes and con-servation strategies to protect other taxa.

The Greenland White-fronted Goose also facesnew and different challenges in the immediatefuture. Global climate change has the potentialto modify the meteorological conditions of thebird throughout its range, and hence the habitatsand phenology of growth of plants which theyexploit. Nowhere is this more of a potential threatthan on the breeding areas, where change is fore-cast to be most dramatic. Model predictions agreethat north-west Greenland will experience coolersummers and therefore increasingly delayedsprings (Zöckler & Lysenko 2000) and there areindications that these patterns are already evident(Rigor et al. 2000). As is discussed in depth else-where in the thesis, there is mounting evidencefor 'leap-frog' migration and segregation amongstthis goose population (MS2, MS6 and see Chap-ter 6). Geese breeding in the south of the breed-ing range tend to winter furthest north and viceversa. Hence, cooling in the north of the breedingrange is likely to affect those geese that winter inIreland and Wales more than those wintering inScotland (MS2, MS27). Breeding success in thepopulation is linked to June temperatures(Zöckler & Lysenko 2000). Some climate modelspredict that central west Greenland (between 67ºand 69ºN) will experience warmer springs whichcould improve conditions for geese breeding there(Rigor et al. 2000, W. Skinner in litt.). This is thearea with the highest densities of summeringGreenland White-fronted Geese, both breedingand moulting (MS23), and is thought to be thesummering area of birds which winter predomi-nantly in Scotland (MS2). It is also the area wherebreeding and moulting Canada Geese have in-creased greatly in recent years (MS13, MS22).During the moult, White-fronted and CanadaGeese use the same habitats and areas adjacentto open water bodies to regrow flight feathers (seechapter 7). Canada Geese there breed in their thirdsummer and produce more young per unit areathan Whitefronts using the same habitats. CanadaGeese are also behaviourally dominant over themthere (Jarrett 1999, Kristiansen 2001). Since Can-ada Geese show no signs of reducing their rate of

0

4000

8000

12000

16000

1950 1960 1970 1980 1990 2000

Census year

Spr

ing

coun

tWexford

Islay

Figure 2.2. Annual spring counts of Greenland White-fronted Geese at the two most important winteringsites, Islay in the Inner Hebrides of Scotland and Wex-ford Slobs in south-east Ireland. The vertical arrowindicates protection from hunting at both sites.

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expansion, they are likely to exert an ever greaterinfluence on the endemic Greenland White-fronted Geese which used to be the only herbivo-rous waterbird in the region. Hence, inter-specificcompetition on the breeding areas could play amajor role in the future population dynamics ofGreenland White-fronted Geese. As many of thenorthern populations of geese continue to expand,use novel habitats and exploit new areas, the po-tential for competitive interactions increases. Theneed for an understanding of such processes inorder to make predictions relating to the impactsof these interactions at the population level makesthis particular study of broader ecological signifi-cance in the future.

What is clear is that the ecological conditions ex-perienced by the geese will not remain constantand the benefits of existing information relatingto population processes will offer some key tounderstanding how Greenland White-frontedGoose numbers will respond to change in the fu-ture. The future changes in distribution and abun-dance of this race of geese will not be any lessinteresting to follow than those in the past.

2.7 Conclusions and discussion

The traditional patchy bogland wintering habi-tat of the Greenland White-fronted Goose un-doubtedly constrained population size in a land-scape unchanged by Man’s activities. Exploita-tion of this specific habitat is likely to have shapedhighly site faithful behaviour and influenced theevolution of the prolonged parent-offspring rela-tionships which distinguishes this populationfrom most other goose species. Whilst habitat

destruction and hunting undoubtedly had a nega-tive effect on population size, the recent coloni-sation of low-intensity agricultural systems andsubsequent use of intensively-managed reseededgrasslands have permitted considerable extensionto an otherwise highly conservative pattern ofhabitat use. Restrictions on winter hunting haveresulted in an increase in numbers since 1982,such that it seems likely that there are now moreGreenland White-fronted Geese than in the re-cent past, strongly suggesting that populationlimitation was previously related to factors oper-ating on the wintering grounds. The provision ofnew improved grassland habitats during the 20thCentury has permitted the colonisation of new,richer food sources by the population. Huntingin the period up to protection may have imposedpopulation limitation on the wintering groundsprior to 1982. Hunting in Iceland is likely to con-tinue to add to overall mortality in the popula-tion. The adequacy of site designation and con-servation in Iceland needs to be considered in thecontext of the annual cycle. Extension of feedingto intensively managed agricultural grasslandsavailable from the late 20th Century onwards hasprobably been responsible for the contemporarylack of population limitation through factors op-erating on the wintering grounds. Under protec-tion, numbers have increased but show new signsof reduction in the rate of increase. New threatsto the population from global climate change andcompetitive interactions with other herbivorousgeese recently colonising their breeding areasunderline the need for continued monitoring ofthe population. It is therefore important to initiatea specific study of the influence of climate on sur-vival and reproduction amongst elements of thepopulation in different parts of the breeding range.

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3.1 Introduction

Greenland White-fronted Geese return each yearto Greenland for the summer. The challenge toeach individual as daylength increases is to at-tain a body condition that will enable it to under-take spring migration, first to Iceland and thenceover the Greenland Ice Cap to the breeding rangeon the west coast. To attain that body conditionwill, at minimum, involve the necessary mechani-cal adjustments to flight architecture and the ac-cumulation of sufficient energy stores to sustainlong distance migratory flight. How are thesestores of protein and fat, respectively, accumu-lated through the winter and spring? When aresuch stores accumulated and what factors mayaffect the ability of an individual to reach the nec-essary minimum levels to start the flight north-wards and to complete it safely? Most geese ofthe genus Anser reach sexual maturity at the ageof 2 or 3 years (Owen 1980). Only a small propor-tion of Greenland White-fronted Geese more thantwo years of age breed successfully (see chapter6). There may be different thresholds of stores ac-cumulated en route to the breeding grounds thatcould affect the ability of an individual to repro-duce successfully. For instance, stores of fat couldbe sufficient to provide a female with fuel for theentire journey and to invest in clutch initiation,but still fall short of the amount required to sus-tain the female through incubation. Under suchcircumstances, the relatively long-lived indi-vidual survives to attempt to breed in a subse-quent year, despite failing to return with youngin this particular season. Inability to accumulatefat stores sufficient to fly to Iceland in the firststage of migration would have a direct impact onthe survival of the individual. The accumulationof body stores in anticipation of events in the an-nual cycle of the geese is therefore of consider-able importance for the fitness of an individualand has consequences for the population, by hav-ing a direct effect on survival and reproduction.

3.2 Spring accumulation of body storeson the wintering grounds

Geese show a predictable rheostasis in body massduring the course of the winter. It is generallyassumed that geese maintain a level of body stores

that represents a trade-off between the likely needto utilise such stores and the costs of maintenance.Most studies of waterbirds have shown a patternof mass accumulation during autumn followedby a decline in winter and an increase in spring(e.g. Mallard Anas platyrhynchus Owen & Cook1977, Dunlin Calidris alpina Pienkowski et al.1979). However, relatively few studies have de-termined the change in body mass of geese at anyone wintering area throughout the entire non-breeding period. In general terms, this representsa cycle of rebuilding depleted stores (generallyof fat) exploited to fuel the often long flight fromautumn staging areas. These fresh stores are hy-pothesised to be accumulated in anticipation ofsevere weather during the middle part of the win-ter. In mid-winter, limits to food intake, short for-aging daylength and low temperatures may com-bine to necessitate the periodic use of such storesto supplement exogenous sources of energy (e.g.Ebbinge 1989, Owen et al. 1992, but see alsoTherkildsen & Madsen 2000). In late winter, de-pletion of these stores often results in lowest lev-els of body mass as daylength increases, followedby a period of rapid accumulation of body massin preparation for the spring migration towardsthe ultimate breeding areas (Owen et al. 1992),although such spring pre-migration fattening isnot typical of all arctic-nesting geese (see Flickin-ger & Bolen 1979, Ankney 1982). Nevertheless, inseveral studied species, female geese may in-crease their body weight by 41-53% over winterlevels (see for example McLandress & Raveling1981).

Not all late winter/spring mass accumulation re-presents fat, since birds about to undertake amajor migration episode after an essentially sed-entary winter period are likely to have to recon-struct their (i) digestive and (ii) flight architec-ture (e.g. McLandress & Raveling 1981, Piersma1990). These modifications enable more efficientaccumulation of reserves and through shifting ofinternal protein reserves, the enlargement ofbreast musculature to sustain prolonged periodsof flight (Piersma 1994). Whether mass changesin winter affect breeding success in geese has yetto be demonstrated, but there are clear links be-tween breeding success and body condition in latespring (e.g. Ebbinge 1989, Black et al. 1991, Mad-sen 1995). Hence, the mass dynamics of Green-

3 Accumulation of body stores and the flight to Iceland

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28

land White-fronted Geese in late winter andspring are at least likely to affect the ability of anindividual to undertake the flight to Iceland suc-cessfully. Furthermore, the levels of stores avail-able on departure from the wintering areas couldpotentially influence the extent of stores availablefor the onward flight to Greenland and ultimatelyfor investment in reproduction. Clearly, any con-tribution that accumulated stores can make tobody maintenance, egg laying and incubation (inthe case of the female) and to territorial defenceand mate protection (amongst males) is likely tocontribute to the reproductive output of a goosepair.

In the case of the Greenland White-fronted Goose,there are three sources of proxy data that can beused to follow the changes in body constituentsor in fat stores throughout the course of the win-ter. The first is the use of catch data from Wex-ford Slobs, where geese have been captured us-ing cannon nets each year since 1983/84. All havebeen aged and sexed and weighed to the nearest50 g before being fitted with individual marks andmetal tarsus rings (see MS7 for full details). Mostcatching has taken place in the autumn, especiallyin October/November, but some birds have beencaught in all months from October to April. Fit-ted regression lines to the full data set of indi-

vidual weight regressed on date shows a polyno-mial relationship between body mass and datefor all age and sex classes (Figure 3.1). These pat-terns represent a slight decline in mass from ar-rival until December followed by a gradual accu-mulation until departure in early to mid April.

These data represent the cumulative data overmany years, but the general trend from Januaryonwards is confirmed by a second method. A se-ries of catches carried out throughout the springof 1999 specifically to assess within-winter pat-terns of body mass change concentrated on latewinter/spring catches of small numbers of pairs.The results are shown in Figure 3.2 and confirmthe general pattern of relatively slow accumula-tion of body mass throughout the latter half ofthe winter at Wexford.

The third proxy method of assessing body massis the use of field scores of abdominal profiles ofgeese wintering at Wexford. Owen (1981) devel-oped the use of abdominal profiles as a non-con-sumptive method of assessing the fat deposits ofgeese in the field. The method depends upon thefact that fat stored in the abdomen is a reliableindex of general fat stores accumulated through-out the body (Thomas et al. 1983), and the levelsof abdominal fat storage can be assessed using a

Adult females

1500

2000

2500

3000

3500

4000

1-Oct 20-Nov 9-Jan 28-Feb 18-Apr

Date of capture

Bod

y m

ass

(g)

Juvenile females

1500

2000

2500

3000

3500

4000

1-Oct 20-Nov 9-Jan 28-Feb 18-Apr

Date of capture

Bod

y m

ass

(g)

Adult males

1500

2000

2500

3000

3500

4000

1-Oct 20-Nov 9-Jan 28-Feb 18-Apr

Date of capture

Bod

y m

ass

(g)

Juvenile males

1500

2000

2500

3000

3500

4000

1-Oct 20-Nov 9-Jan 28-Feb 18-Apr

Date of capture

Bod

y m

ass

(g)

Figure 3.1. Body mass determinations of Greenland White-fronted Geese caught at Wexford during the winters1983/84-1998/99 combined, showing fitted polynomial regressions (see Appendix 1 for statistics relating tofigures1).

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29

predetermined visual scoring system. In Green-land White-fronted Geese, there is a good corre-spondence between this measure and overallbody mass (see chapter 4). This method of assess-ing changes in abdomen profile has been appliedto collared individual Greenland White-frontedGeese wintering at Wexford Slobs since 1984/85,enabling the compilation of median field scoresfor each half-month period there over many years.These values are presented in Figure 3.3, whichdemonstrates a remarkable degree of betweenyear variation in arrival condition of birds in au-tumn, but a high degree of convergence towardsattainment of similar scores by the time of thespring departure. Combining all years suggestslittle difference between the sexes in the rate ofaccumulation of abdominal fat stores (Figure 3.4).The patterns of change in this measure are verysimilar to those of direct body mass determina-

tion, suggesting that geese only gradually accu-mulate fat deposits over the period from midDecember until their departure in mid April.

It would therefore seem that unlike other stud-ied geese in winter (e.g. Svalbard Barnacle Geesewintering in western Scotland, Owen et al. 1992),Greenland White-fronted Geese at Wexford aregenerally able to maintain and even increase bodymass during the short day lengths of Decemberand January. This is probably due to the gener-ally mild prevailing weather conditions and fa-vourable feeding conditions at Wexford, whichprobably reflects conditions throughout much ofthe winter range. Mayes (1991) showed that onlywhen ambient temperatures averaged –0.5ºC inJanuary 1985, and the frozen substrate precluded

geese from probing for nu-tritious stolons, did Green-land White-fronted Geeselose condition at a semi-nat-ural grassland site. Similar-ly, Stroud (unpubl. data)studying Greenland White-fronted Geese on Islay foundmedian API scores fell by1.4-2.0 units during the sub-zero temperatures of De-cember 1980. Prolongedperiods of frost and tem-peratures to –10ºC at thattime stopped grass produc-tion and denied geese ac-cess to peatland food itemsat the roosts.

2000

2500

3000

3500

21-Oct 20-Nov 20-Dec 19-Jan 18-Feb 19-Mar 18-Apr

Date of capture

Bod

y m

ass

(g)

adult male

adult female

1999 females

1999 males

Figure 3.2. Body mass determinations of individualadult male and adult female Greenland White-frontedGeese caught at Wexford in spring 1999, compared toregression models for these age and sex classes from1983/94-1998/99 combined (from Figure 3.1).

0

1

2

3

4

early

Oct

late

Oct

early

Nov

late

Nov

early

Dec

late

Dec

early

Jan

late

Jan

early

Feb

late

Feb

early

Mar

late

Mar

early

Apr

late

Apr

Med

ian

abdo

min

al p

rofil

e sc

ore

1984/85

1985/86

1986/87

1987/88

1988/89

1989/90

1990/91

1991/92

1992/93

1993/94

1994/95

1995/96

1996/97

1997/98

1998/99

Figure 3.3. Half-monthly median abdominal profile scores of Greenland White-fronted Geese wintering at Wexford Slobs, SE Ireland during the years 1984/95-1998/99.

0

1

2

3

4

early

Oct

late

Oct

early

Nov

late

Nov

early

Dec

late

Dec

early

Jan

late

Jan

early

Feb

late

Feb

early

Mar

late

Mar

early

Apr

late

Apr

Med

ian

abdo

min

al p

rofil

e sc

ore

female

male

Figure 3.4. Half-monthly median abdominal profilescores for adult male and female Greenland White-fronted Geese wintering at Wexford Slobs, SE Irelandfor all years combined 1984/95-1998/99.

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30

Because the winter range of the Greenland White-fronted Goose falls within the 3ºC January iso-therm (Belman 1981), the population rarely en-counters periods of prolonged ground frost.Hence, although relatively low temperatures maystop or reduce grass growth, their propensity forgrubbing and probing in soft substrates in semi-natural grass swards for stolons and nutrient richoverwintering plant parts (e.g. bulbils, rhizomesand other storage organs) enables the geese tomaintain a nutrient and energy rich diet fromDecember onwards. In addition, the mild oceanicconditions of their winter range reduces the costsof thermoregulation compared to, for instance, theRussian-breeding White-fronted Geese whichwinter in continental Europe (Mooij et al. 1999).Hence, the need of the Greenland White-frontedGeese to accumulate substantial stores necessaryto balance the nutrient shortfalls in mid-winter(as a result of restricted food availability, feedingopportunity and/or enhanced energetic expendi-ture) may be less than in other waterbirds (e.g.Owen & Cook 1977, Pienkowski et al. 1979,Ankney 1982, Ebbinge 1989, Owen et al. 1992).

These data suggest that Greenland White-frontedGeese at Wexford do not rapidly accumulatestores in preparation for the spring migration toIceland, as they have maintained conditionthroughout the autumn and early winter period,accumulating stores for migration over an ex-tended four-month period. Nevertheless, birds doaccumulate mass in late March and through Aprilfaster than at other times during the winter. Thisis still not as dramatic as in the Barnacle Geesethat winter in southwest Scotland and migrate

first to stage in northern Norway before continu-ing northwards to their Svalbard breeding areas(Owen et al. 1992). Similarly, the Dark-belliedBrent Geese Branta b. bernicla show very muchmore rapid spring fattening immediately prior tomigration from Western Europe to staging areasin the White Sea (Ebbinge 1989, Drent et al. 2000).

3.2 The costs of the flight to Iceland

Can we predict the amount of fat deposits a Green-land White-fronted Goose must accumulate in or-der to fuel the flight from the wintering groundsto the staging areas in Iceland? First, we have tounderstand something about the nature of themigration flights between wintering areas andspring staging sites: how far do geese fly, howfast and how often do they rest? In 1997, a projectwas started to affix satellite transmitters to Green-land White-fronted Geese on the wintering areasin Ireland in order to track the migratory behav-iour of known individuals en route to their sum-mering areas (MS20). The regular signal producedby the radio transmitter is detected by orbitingsatellites above that enable the precise positionof the transmitter to be determined at given in-tervals. In this way, it is possible to track the mi-gration routes, duration and speed of individualGreenland White-fronted Geese moving from Ire-land to Iceland and subsequently from Iceland totheir ultimate breeding areas in west Greenland.These studies showed that the geese flew directlyfrom Ireland to staging areas in Iceland in threedifferent springs along a narrow migration corri-dor. All maintained ground speeds of 50-90 km

Table 1.1 Estimated fat requirements (in g.) for the flight in still air of a male and female Greenland White-fronted Goose from Wexford, Ireland to Hvanneyri, western Iceland on spring migration, based on fourdifferent formulae (see text for further details).

Flight speed(km/hr)

McNeil &Cadieux (1972)

Summers &Waltner (1978)

Greenewalt(1975)

Davidson(1984)

Malelean mass 2.6 kg

Femalelean mass 2.3 kg

50

60

70

80

90

50

60

70

80

90

268

221

188

164

145

246

202

172

150

132

252

208

178

155

138

237

196

167

146

130

292

292

292

292

292

272

272

272

272

272

254

211

180

157

139

240

199

170

148

131

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31

h-1 and none showed any sign of resting on thesea en route.

A number of different approaches have beenmade to estimate the energetic costs of flights forbirds of different sizes. The simplest approacheshave been those methods, which use crude esti-mations of the energetic costs of flight. Based onsimple energetic formulae, it is possible to esti-mate the costs of flight to Iceland from Wexford.Given that many Wexford wintering birds stageat Hvanneyri in western Iceland (MS27), the dis-tance between these two areas (1,500 km) wasused to calculate the minimum flight range nec-essary for geese to reach their staging site. Thestill-air flight-range estimation methods ofMcNeil & Cadieux (1972), Summers & Waltner(1978), Greenewalt (1975) and Davidson (1984)were used to back-calculate the minimum fatstores necessary to sustain flight over that dis-tance. These were used to generate a range of dif-ferent speeds for a female of departing lean bodymass 2.3 kg and a male of 2.6 kg (see Table 3.1).Given the observed ground speeds of 50-90 kmh-1 observed amongst satellite tagged geese mak-ing this journey, a range of values were obtainedfor these observed speeds. These suggest thatmales require between 145 and 292 g of fat andfemales 130-272 g fat to fuel the passage fromWexford to Hvanneyri.

A more sophisticated method is to attempt tomodel the birds rate of use of fuel, based on themechanical work the organism must do, given itsmorphology and the conditions of flight. This isthe aerodynamic approach of Pennycuick (1989),which makes several assumptions about thephysiology of flight, but nevertheless provides thebest predictive model available at the present. Themost recent version of his software (Flight.basversion 1999) was used which incorporates find-ings from recent wind tunnel studies which sug-gest that even for a large birds like a goose, thecoefficient of body drag (Cdb) is lower than previ-ously thought (Pennycuick et al. 1996). In thepresent analysis, the suggested lower value (Cdb= 0.10) was used instead of 0.25 (see also Green &Alerstam 2000). The results are shown in Figure3.5, showing the range of flight range estimatesfor a female of lean body mass 2.3 kg and male oflean body mass 2.6 kg, the 1500 km flight neces-sitating 340g and 349g of fat for the male and fe-male respectively. Both calculations make the as-sumption that the geese fly at maximum rangespeed, which was 99 and 103 km/hr respectively.

At lower speeds, for the same total energy ex-penditure, the flight range estimate would be re-duced (Figure 3.6).

Despite considerable monitoring efforts, it is clearthat we still know very little about the prelude todeparture of the geese from their winteringgrounds in spring. All of the data presented abovederive from the main Irish wintering site, andnothing is known from wintering sites elsewhere.Satellite telemetry (MS20) showed that in a springwhen a relatively early departure occurred fromWexford, at least one of the early departing birdsfitted with a transmitter left Wexford on 10 April1997, but staged on the northern Ireland coastuntil 16 April before departing for Iceland. Suchspring staging within Ireland may be simply dueto birds responding to initial cues, which sug-gested that weather conditions were favourablefor migration, only to encounter unfavourableconditions later on. Resightings of Wexford-win-tering birds seen soon after spring departure on

1000

1100

1200

1300

1400

1500

1600

1700

50 60 70 80 90 100 110

Flight speed (km/hr)

Flig

ht r

ange

(km

)

Figure 3.6. Effects of differences in flight speed on thetheoretical flight range of Greenland White-frontedGeese.

Figure 3.5. Theoretical flight range estimates for maleand female Greenland White-fronted Geese of leanbody mass 2.6 and 2.3 kg respectively, given differentfat loads at point of departure based on Pennycuickmodels (see text for details).

1000

1200

1400

1600

1800

0.2 0.25 0.3 0.35 0.4 0.45

Fat deposits at departure (kg)

Flig

ht r

ange

bur

ning

fat o

nly

(km

)

Male lean mass 2.6 kg

Female lean mass 2.3 kg

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32

the Outer Hebrides and Islay in Scotland suggestsgeese have the option to stop off at more north-erly staging areas within Britain and Ireland af-ter departure from further south (for whateverreason). Certainly there was evidence in 1997,1998 and 1999 that geese departed from Wexfordshortly after the wind had swung to a southerlydirection (MS20). Geese are likely to save consid-erable energy by using a following assisting windcompared to making the flight with head- orcrosswinds. A full analysis of prevailing meteoro-logical conditions associated with migration epi-sodes is currently underway, as is a full analysisof the energetic costs of the migration from Wex-ford to staging sites in Iceland.

3.3 The mass gains in Ireland duringwinter

From the catch data, it is possible to estimate fromthe fitted regression models the difference in bodymass between the lowest mean weight (the pointof minimum inflection derived by differentiationfor the model) and the mean weight around nor-mal departure time (taken to be April 20). Thedifference is 3077-2690 = 387 g for males (14% in-crease) and 2787-2380 = 407 g for females (17%increase). It is unlikely that mid-winter weightsrepresent fat-free mass. Stroud (unpubl. data)found significant deposits of mesenteric fat in dis-sections of Greenland White-fronted Geese shoton Islay throughout the winter. Between 9 and 48g of fat of this form (0.3-1.9% body mass) were re-covered from individuals throughout January(D.A. Stroud in litt.), although measures of otherfat deposits were not available from these birds.

McLandress & Raveling (1981) found that 61% ofweight gain between mid winter and spring mi-gration departure in male Giant Canada GeeseBranta canadanesis maxima was lipid and 47% infemales. Corresponding proportions of fat inweight gains for migrating waders vary between50 and 100% (see Zwarts et al. 1990), with meas-ured values of between 60% (McNeil 1969, 1970)and 90% (Summers et al. 1987, 1989). However, itis unlikely that all of the difference in mass ac-counted for is fat, indeed larger birds (such asgeese) tend to incorporate a greater proportionof non-fat components when increasing bodymass (Lindström & Piersma 1993). In the Green-land White-fronted Goose, 60-90% of the weightincrease representing fat would represent an ac-cumulation of 232-348 g fat in males and 244-366

g in females. Mid-winter weights of White-fronted Geese in North America include 12-16%fat content, which would equate to an additional286-381g of fat in females and 323-430g in males.Although these calculations make a number ofimportant assumptions, on this basis, the total av-erage fat content of Greenland White-frontedGeese on departure could constitute sufficient en-ergy source to sustain the flight to Iceland usingfat only as a source of energy. Based on these aver-age values, geese also have the potential to supplythe energy needs from stores for self-maintenancein Iceland for several days after arrival, should theyencounter restricted feeding opportunities.

3.4 Conclusions & discussion

Greenland White-fronted Geese show variablelevels of body mass throughout the season, butunlike the few other studied populations, at Wex-ford they maintain, or only slightly lose massthrough mid-winter. After mid December, massis accumulated increasingly until departure inmid-April. On the basis of various theoreticalapproaches, geese need to amass fat stores of 150-340 g (females) and 139-349 g (males) to fuel theflight to staging areas in Iceland. If it is assumedthat (i) mid-winter minimum body mass repre-sents lean body mass (unlikely based on otherbody composition studies of A. albifrons) and (ii)that 80-90% of the increase to departure weightrepresents fats store accumulation, based on av-erage body mass determinations, then GreenlandWhite-fronted Geese attain sufficient fuel for thespring flight to Iceland. If the minimum mid-win-ter mass includes fat reserves, geese retain sub-stantially more fuel than required for the journeyto Iceland. However, the distance involved meansthat the geese could not fly direct to Greenlandfrom the wintering grounds, a distance of morethan 2600 km.

More detailed analysis of the satellite telemetrydata, incorporating real-time meteorological con-ditions prevailing at the time of the migrationepisodes, is required to determine the preciseenergy requirements of the geese during thesespecific migration flights. It would be highly in-structive to use heart beat as an alternative meth-od to independently measure fuel consumptionduring migratory flights (as used by Butler et al.1998). Until full analysis of the fat dynamics ofWhite-fronts is carried out (e.g. using non-de-structive techniques such as the use of doubly

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33

labelled water), the precise extent, duration andrate of fat store deposition on the winteringgrounds prior to migration cannot be accuratelydetermined. Similarly, there is a need to deter-mine changes in organ size associated with thisperiod of body mass gain to determine what otherchanges in body state occur during the preludeto migration. Since it is to be expected that anumber of external factors affect the rate at whichindividuals accumulate these fat and other stores(e.g. human disturbance, access to feeding oppor-

tunity as a result of social status, differences inhabitat quality and predation risk) it would behighly instructive to co-ordinate such studies onindividuals in differing wintering situations. Be-cause of great variation in habitat quality on thewintering grounds and the apparent differencein trends in numbers at the different resorts, it isimportant to establish the role these factors playin determining survival, emigration and fecun-dity rates amongst these different elements of thepopulation.

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4.1 Introduction

Until the 1980s, little was known about the statusof staging Greenland White-fronted Geese in Ice-land. It was known that large numbers passedthrough Iceland in autumn, but now it is knownthat the population also stops there in spring enroute to the breeding grounds (MS4). It is clearlyimportant to establish whether, where and forhow long birds stage on spring migration sincefeeding at staging sites enables individuals to re-coup depleted energy and nutrient stores andhence potentially affect subsequent breeding suc-cess (see review by Thomas 1983). Weather con-ditions in Iceland in spring had been shown tocorrelate with subsequent breeding success of thePink-footed Geese Anser brachyrhynchus whichnest there (Fox et al. 1989). Hence, it was reason-able to assume that weather conditions and theavailability of forage were likely to affect the con-dition of migrating Greenland White-frontedGeese departing for the breeding grounds fromIceland in spring. During the late 1980s andthroughout the 1990s, a series of studies were car-ried out examining the spring staging of differ-ent goose species in Iceland, to assess the impor-tance of feeding ecology of pre-nesting stagingin that country. An important aim was to estab-lish the importance of specific staging areas andto assess the distribution and abundance of thedifferent goose populations there, examining theuse of different habitats and the way in whichthe geese exploit these (e.g. Boyd & Fox 1992,1995, Fox et al. 1991, 1992, 1994a, 1994b, 1999). Invery recent years, these studies have involved aPh.D study (Kristiansen 2001) and Masters stu-dent study (Nyegaard 2001), but from which se-lected results are presented here.

In conservation terms, the most important ele-ments in the study of spring staging relate to theidentification of staging areas, the habitats andfood plants used by the geese, the level of ener-getic gain that can be achieved by geese utilisingdifferent habitat types and how they may derivethe maximum nutritional benefit from them. Inthis way, it is possible to establish some basis forranking the importance of sites and habitats interms of the number of birds using different sitesfor site safeguard and nature conservation man-agement purposes. Finally, studies have also con-

sidered how much nutrient gain can be derivedfrom the staging period in Iceland during the prel-ude to migration over the Greenland Ice Cap tothe breeding grounds on the west coast.

4.2 Distribution of spring stagingGreenland White-fronted Geese inIceland

Observations from many years confirm that alarge proportion (if not all) Greenland White-fronted Geese stage in Iceland from c. 10 April toc.12 May in most seasons (MS4, MS19). At thistime, they use two main areas, namely the south-ern lowlands (Árnessýsla, Rangárvallassýsla andVestur-Skaftafellssýsla) and the western lowlands(Kjósarsýsla, Borgarfjarðarsýsla, Mýrarsýsla andSnæfellsness- og Hnappadalssýsla). Spring mi-gration phenology appears to differ between ar-eas, with earlier arrivals but a slower build-up tomaximum numbers in the southern lowlands.Here, numbers peaked during 24-26 April in 1990-1992, but dispersed earlier compared to the rapidbuild up in western staging areas to peak num-bers during 18-22 April in 1997-1999, where sub-stantial numbers of birds remained well into Mayeach year (MS19). These differences most likelyrelate to the timing of migration in the years con-cerned, but could also reflect different migrationstrategies of birds using the two areas (records ofindividuals using both staging areas are rare,MS27). The southern lowlands, especially alongthe coast, experience a slightly milder climate andhence earlier thaw than the west, which may ini-tiate plant growth a little earlier in the spring. Inaddition, there are substantial areas of tillage inthe southern lowlands that do not occur in thewest (see below).

At the most important staging site in the westernlowlands, Hvanneyri, up to a maximum of 1,600birds have been counted (MS19). Based on obser-vations of individually marked birds at Hvanney-ri, more than half of the geese remained for lessthan a week, mostly early on in migration, whilstmore than a third stayed for almost the entire stag-ing period (c. 24 days).

From observations of individually marked Green-land White-fronted Geese, at least 90% of goslings

4 Spring staging in Iceland and the flight to Greenland

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36

associate with their parents and siblings in Ice-land in their first spring. All reported subse-quently have been seen within 4 km of where theywere seen in their first spring with their parents(MS27). As on the wintering grounds (MS7, MS9),individuals show a high degree of within- andbetween-season site fidelity in Iceland. Some 96%of multiple within-spring resightings of individu-als were within 4 km of each other, although 3geese moved 88 km from the southern to the west-ern staging areas. Four percent of geese seen intwo consecutive springs and none seen in con-secutive autumns moved more than 4 km be-tween years. By contrast, significantly more (12%)moved more than 4 km in subsequent seasonsbetween spring/autumn and autumn/spring. Allthese shifted within the western lowlands to orfrom Hvanneyri in autumn, the only declaredhunting-free area for Greenland White-frontedGeese which are otherwise legal quarry through-out Iceland in autumn. Scottish-wintering birdswere more likely to use southern staging areasand generally Wexford (Ireland) wintering birdswere more likely to stage in the western lowlandsof Iceland in both spring and autumn (MS27).Since Scottish wintering birds tend to breed in thesouth and central part of the breeding range, andWexford-wintering geese generally summer inthe north of the range, there may be some basisfor genetic isolation amongst different elementsof the population (MS2, MS6). The methods usedin this investigation are likely to overestimate lev-els of between season site fidelity, so these resultsshould be interpreted with caution. The use ofother independent methods (such as the use ofdata from satellite tagged individuals) is neces-sary to validate current estimates.

4.3 The costs of the flight to Greenland

Based on the results of the satellite telemetryproject, Greenland White-fronted Geese flew an-other 1,500 km from the west Iceland staging ar-eas to their arrival points in west Greenland(MS20). The energy requirements necessary tocomplete the flight would be the same as the Ire-land-Iceland flight, if the geese did not have tocross the Greenland Ice Cap. In the early 1980s, itwas unknown whether geese did traverse the IceCap, or rather migrated along the west coast toand from the southern most point. Since that time,it has been shown that such a long journey aroundKap Farvel to avoid climbing to cross the interiorice offers no increased efficiency to migrating

geese (Gudmundsson et al. 1995). Radar obser-vations and investigations have shown that geesecross the Ice Cap in both spring and autumn (K.Vægter, pers. comm., Alerstam et al. 1986). Thesatellite tagged individuals took this route inspring, passing over the Greenland Ice Cap wherethis reaches to c.2,800 m above sea level (MS20).Therefore, geese would also have to expend theenergy required to climb to this altitude. Given afemale goose starting this climb with a body massof 2.3-2.9 kg and a male of 2.6-3.3 kg, the forcerequired to lift these masses to 2800 m would be6.3-8.0 x 104 Newtons for females, and 7.1-9.1 x104 for males. If it is assumed that there is an en-ergy conversion efficiency of 0.23 and that aero-bic bird flight is fuelled by fat (with an energydensity of 3.9 x 104 J g-1, Pennycuick 1989), this isequivalent to an additional 70-89 g of fat for fe-males and 80-101 g of fat for males to accomplishthe additional physical work required to fly upand over the Ice Cap. On this basis, the fuel re-quirement to make the second leg of the springjourney would be between 200 and 429 g for fe-males and 219-450 g for males.

The accumulation of stores in Ireland in prepara-tion for the flight to Iceland is dispersed over al-most 4 months. At similar rates of accumulation,the mean stopover time in Iceland does not per-mit the geese to achieve similar rates of gain dur-ing the average of 18 days the satellite taggedgeese remained there in spring (MS20). We needto know how fast geese can potentially accumu-late stores in Iceland, and in order to do so, weneed to understand something about their bodycondition immediately after arrival in Iceland,track the rate of change and assess their depart-ing condition at the time they set off for WestGreenland. Furthermore, we need to be able toassess whether different feeding strategies adopt-ed by the geese enable some individuals to betteraccumulate stores than do others.

4.4 Mass gains in Iceland in spring

We have two independent means of assessing thespring accumulation of body mass during thestopover of Greenland White-fronted Geese inIceland. Geese were captured at Hvanneyri in1999 throughout the spring staging period. Thechange in body mass of adult males and femaleswith time are shown in Figure 4.1. The best fitregression model was a simple linear form. Basedon these models and an average arrival date of

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20th April 1999 (MS19), the average body massesof arriving birds were 2.75 kg (adult males) and2.51 kg (adult females). Assuming that the birdsarriving at Hvanneyri were a representative sam-ple of those departing Wexford, this meant thatin 1999, geese arriving in Iceland had used 327 gand 277 g of fat respectively, assuming all the dif-ference to be fat. This is slightly less than predictedby the Pennycuick calculation, but more than bythe energetic flight range methods. However,these calculations are based on average values,and may not represent the true situation duringthe 1999 spring migration episode. These esti-mates suggest that the geese had not depleted allthe reserves accumulated over the mid-winterminimum body mass in Ireland (see chapter 3).Using the same regression models, and a meandeparture date of 5th May 1999 (MS19), geeseaccumulated an average of 369 g (15% in adultfemales) and 451 g (a 16% increase in body massin adult males) during their 15-day stay in Ice-land. These data are based upon observed lengthsof stay of collared birds at Hvanneyri, which wereslightly shorter than the average for the satellitetagged individuals. Nevertheless, the accumula-tion of 24.6 and 30 g body weight per day for fe-males and males respectively is impressive dur-ing this short stopover. Their estimated meandeparture masses were thus 3.21 and 2.88 kg (for

adult males and females) when departing for westGreenland from Hvanneyri, 129 and 96 g respec-tively heavier than the departure mass from Ire-land.

An alternative approach is to establish a calibra-tion factor for field scores of abdominal profiles,based on the body mass of known individuals ofknown abdominal profile scores. There was agood correlation between the API score and bodymass amongst the geese caught at Hvanneyri (Fig-ure 4.2). Since large numbers of geese were scoredevery day at Hvanneyri (although not specificallyassigned to sex class), this enables the generationof mean body mass values for geese staging atthe farm using the relationships shown in Figure4.2 and assuming a sex ratio of parity. The resultsof this are shown in Figure 4.3. Mass accumula-tion does not appear linear (as suggested by catchdata alone), suggesting that the catch data mayactually slightly underestimate mass accumula-tion by the end of the staging period. Because thecaught birds were cannon-netted over bait, itcould be that the capture technique selected forbirds in poor condition attracted to rich sourcesof food.

Despite the many assumptions made in these sim-ple calculations, it does appear that geese arrivedin Iceland with a residue of the body stores accu-mulated on the winter grounds and then veryrapidly increased body mass there. If it is assumedthat the geese at Wexford are typical of those else-

Males

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(g)

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04-15-99 04-20-99 04-25-99 04-30-99 05-05-99 05-10-99

Date of capture

Bod

y m

ass

(g)

Figure 4.1. Changes in body mass of staging adult maleand female Greenland White-fronted Geese caught atHvanneyri, west Iceland in spring 1999. Fitted regres-sion lines are best fit least squares linear regressionmodels.2

Adult Males

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Adult Females

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ass

Figure 4.2. Relationship between abdominal profilescore and body mass of captured adult male and fe-male Greenland White-fronted Geese at Hvanneyri,spring 1999.3

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38

where in the wintering range and that all geeseaccumulate mass at the same rate as those cap-tured, the geese departing Hvanneyri left with516 g (adult males) and 503 g (adult females) morebody mass than the mid-winter minimum masslevel. Assuming this increase includes 60-90% fat,departure fat stores would amount to 302-453 g(females) and 310-464 g (males). Again, this cer-tainly underestimates the true extent of fat de-posits, since mid-winter mass is unlikely to rep-resent lean mass levels. Abdominal profile meas-ures suggest this may underestimate slightly thetrue rate of increase amongst the geese atHvanneyri. Given that a substantial proportionof this accumulation in Iceland was required torestore fat depots and that the mid-winter mini-mum mass included some fat reserves at thattime, this is a substantial and adequate source offat to fuel the crossing of the Denmark Strait andice cap to the summering areas beyond.

4.5 Habitat utilisation in Iceland inspring

Greenland White-fronted Geese probably tradi-tionally used as their natural food source thelower stem storage organs of Eriophorum angusti-folium and Carex lyngbyei that grew in abundancein the lowland wetlands as their natural foodsource (MS4, MS19, MS27). Although the area ofintact mire and undamaged wetland in southernand western Iceland remains large, despite muchdrainage in the 1970s and 1980s, it is clear thatmost spring staging Greenland White-frontedGeese now exploit agricultural grasslands. Themost favoured grasslands are short-cropped hay-

fields that offer the most open dense swards,which exhibit rapid growth in spring. The geeseglean waste from the harvests of previous autumnsin the form of potatoes (especially in the Þykkvibærarea of Holt) and barley (especially in theHvolsvöllur area in Hvolhreppur) in the southernlowlands, as these are released from the wintersnow prior to ploughing. Such crops are not culti-vated to any great extent in the west (MS24).

The results of detailed studies at Hvanneyri haveshown that spring staging geese differentiate be-tween different grassland sward types on the ba-sis of food quantity and quality (MS15, MS16,MS24, MS25, MS26, Nyegaard 2001). The geesefeed on all three of the most abundant grass spe-cies occurring in the sward, namely Phleum pra-tense, Poa pratensis and Deschampsia caespitosa, buteach species is exploited in different ways and atdifferent times according to growth form. Alope-curus pratensis also occurs, but is not especiallyfavoured by the geese.

The fields at Hvanneyri can be classified as beingdominated by one or other species of grass (whereone species constitutes more than 50% of thesward) or are co-dominant (i.e. where 2 speciesof grass differ by less than 20% in their coverage).Combining cumulative goose counts from all clas-sified fields at Hvanneyri shows that Phleum sup-ports significantly greater densities of geese thanPoa, Deschampsia or Alopecurus dominated fields(see Figure 4.4), although the last species was onlypresent in very mixed swards on 5 of the fields. A

Figure 4.3. Comparison of change in daily median ab-dominal profile scores of Greenland White-frontedGeese recorded in the field and back converted to bodymass from the calibration curves shown in Figure 4.2,compared with fitted regression models for change inbody mass obtained from catches (shown in Figure4.1).

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Sward category (dominant species in sward)

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ulat

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e us

e pe

r ha

Figure 4.4. Cumulative goose use of fields of differentsward composition, expressed as total geese per hec-tare (+ SE) during the spring staging period at Hvan-neyri in 1997. Swards were composed of dominantPhleum pratense, Poa pratensis, Deschampsia caespitosaand Alopecurus pratensis or co-dominant Poa/Des-champsia as indicated.

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similar pattern can be seen based upon meandropping densities (as an alternative assessmentof goose use) in plots of sown single speciesstands of different grass species on trial plotswithin one field at Hvanneyri in 1997 (Figure 4.5).Note that the young establishing Deschampsiacaespitosa formed a continuous open sward priorto tussock development and for this reason wastherefore probably as attractive to geese as Poa.

The total goose use of any particular field can beseen as the product of 4 elements over time:

1) food density (which in turn determines thesettlement density of geese)

2) food intake rate (which determines food de-pletion rate)

3) the 'giving up' density of food (the thresholdat which the food resource is depleted to thepoint where it is more profitable to forage else-where)

4) the rate of regrowth of forage plants (whichdetermines the time until the food resourceexceeds the 'giving up' density of food andgeese return for sequential harvesting

In the context of individual field units, contain-ing grasslands of different sward composition, thesettlement density represents the aggregative re-sponse of geese as predators to their 'prey' (i.e.grass blades, MS26). The length of stay of geesein that field represents the interaction betweenstanding crop biomass and intake rates (i.e. therate of depletion of prey items down to a thresh-old 'giving-up' density). Finally, the length of ab-sence is defined by the regrowth rate and qualityof the prey to the point where this exceeds a prof-itability threshold for the geese, at which time

they will return in appropriate numbers to regrazethe accumulated green biomass regrown in theirabsence.

The three major grass species differ in their qual-ity, biomass accumulation and growth pattern.The Phleum is an ecotype introduced from Nor-way, valued for its early season growth, whichcommences before other grasses begin aboveground production. Even in the early stages ofgrowth, this species responds to defoliation bygeese by increasing leaf elongation and elevatedprotein levels, a feature which together with itsgrowth form, makes it the most attractive foragespecies for sequential harvesting by geese (MS15,MS25, MS26). After reseeding of a field withPhleum, leaf densities are high, but as the tussock-forming Deschampsia and the stoloniferous Poainvade, densities of Phleum decline rapidly (Fox1993). In the early stages of the spring stagingperiod, geese therefore assort themselves in re-sponse to the shoot densities of this, the mostabundant green plant material available (MS26),although geese select for the longest leaves(MS25). As a consequence, highest densities ofgeese tend to settle on Phleum fields and eat outmost leaves of suitable length, returning onlywhen regrowth has occurred above a thresholdbite size (Figure 4.6, MS15).

Poa grows at very low leaf densities and althoughof moderate nutrient quality, its later and (in someyears) faster growth rate results in supportinglower densities of grazing geese throughout thestaging period (unpublished data). In contrast toPhleum, where the high quality (low fibre, highprotein) youngest leaf is always removed, leav-

Phleum

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and clover

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psiacaespitosa

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rubra

Agrostis

tenuis

Festuca

pratensis

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pratensis

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psiaberingensis

Goo

se d

ropp

ings

/m2

Figure 4.5. Dropping density (as an index of goose use+ SE) of pure sown stands of different grass species inseed trial plots in a single field at Hvanneyri fromspring 1997.

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Field 48

Phleum fields

Figure 4.6. Cumulative goose use of five hayfieldsdominated by Phleum pratense at Hvanneyri in spring1997. Note the rapid exploitation episodes, followedby short periods with reduced or little exploitation.

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40

ing the photosynthetically active older leaves in-tact, defoliation of Poa invariably removes thelongest green leaf, with subsequent regrowth ofthe youngest blade (Therkildsen & Madsen 1999).Regrowth is generally moderate, but the low den-sity of plants results in low goose densities whichare maintained throughout the staging period,with little sign of sequential harvesting evidentin the other species (Figure 4.7).

Deschampsia has a slow and asymmetric growthform, developing highest densities of fastestgrowing leaves on the south-facing sides of tus-socks (MS16). Although the leaves have high pro-tein content, they are slow to develop, and thepatchy nature of the tussock form and the highlevels of litter associated with Deschampsia-domi-nated fields results in low biomass and slowregrowth rates after defoliation. After such a fieldhas been exploited, there is a long delay beforegeese return to graze the slowly accumulatingregrowth (Figure 4.8).

Not only are the grass sward types utilised dif-ferently and hence support different goose den-sities, but individual geese show differences intheir use of sward types (Figure 4.9). Birds suchas 0CY and 2MY specialised on Poa fields andwere consistent between years, 3KJ spent mosttime foraging on Phleum dominated fields, despitetheir overall rarity (there being only 5 or 6 suchfields out of 62 in all three years of the study).H4A mainly exploited Deschampsia fields. OnlyD9X, a gosling hatched in 1996, associating withits one surviving parent and two siblings in all 3springs, showed any great sign of change in swardselection. In 1997, it was associated with the six

Alopecurus fields, but used Phleum increasingly inthe following years.

It is far from clear whether these patterns of useare more the result of the restricted home rangesof the individuals concerned than habitat selec-tion per se. In all three years of observation, 0CYand 2MY were confined to the same 11 and 12fields respectively and 3KJ was only ever reportedfrom 5 adjacent fields in 1997 and 1998. By con-trast, D9X and associated family members wererecorded using 23 different field units in the threesprings they were observed, with no overlap inhome range between 1997 and the following twosprings (when their use of fields was restricted to11 fields with a higher degree of overlap). Wheth-

0

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Date

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enta

ge g

oose

use Field 35

Field 37

Field 38

Field 39

Poa fields

Figure 4.7. Cumulative goose use of four hayfieldsdominated by Poa pratensis at Hvanneyri in spring1997. Note the lack rapid of exploitation episodes butmore constant exploitation throughout the stagingperiod.

Figure 4.8. Cumulative goose use of five hayfieldsdominated by Deschampsia caespitosa at Hvanneyri inspring 1997. Note the very short intense exploitationepisodes, followed by long periods of little or no ex-ploitation.

0

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Date

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Field 12

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Deschampsia fields

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8

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9Per

cent

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of s

war

d ty

pes

Alopecurus

Phleum

Deschampsia

Poa

Figure 4.9. Use of different hayfield sward types byindividually collared Greenland White-fronted Geesestaging at Hvanneyri in more than one spring during1997-1999 inclusive. Birds are identified by the 3 let-ter/digit collar code and the years of observations.Note the consistency of sward use by 0CY, 2MY, 3KJand H4A in the years of observation that reflect con-sistency of field use as well as sward type. D9X (a ju-venile with its parents in 1997) increasingly usedPhleum dominated fields over the period.

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er 3KJ was a behaviourally dominant individualable to win agonistic encounters in order to re-tain access to the Phleum fields, or whether therare forays of H4A into Phleum swards were sim-ply lack of experience or knowledge is impossi-ble to determine. Aggressive encounters betweengeese were very rarely observed away fromsources of water, so it seems unlikely that overtinterference determines access to highest densityor highest quality food (MS26). Nevertheless,there is no doubt that the use of different swardsin different fields has some effect on the rate ofaccumulation of body stores for the next migra-tion episode onwards to west Greenland (MS18,Nyegaard et al. 2001). Hence, it would appear thatthis presents a potential mechanism by whichdifferent individuals, staging on the same farm,exploiting different fields, may depart from Ice-land having accumulated different levels of bodystores because of their access to different hayfieldsduring their period of spring staging.

We still know very little about the extent andimportance of feeding on natural wetlands in Ice-land. Certainly the rhizomes of Carex lyngbyeihave a very high metabolizable energy contentin spring (McKelvey 1985) and it is important inthe nutritional ecology of other northern water-fowl (Grant et al. 1994). Significant numbers ofGreenland White-fronted Geese feed on Carexmeadows, especially in the middle part of thestaging period in the Borgarfjörður region wheresuch habitat is extensive. This suggests that thishabitat could be an important supplement tograssland feeding, either for the population as awhole, or perhaps for individual birds that spe-cialise on this food. The same is true for theEriophorum angustifolium-dominated wetlands,where it is known that some birds exploit thisfood in the absence of alternative grasslands (be-cause such hayfields do not exist in the vicinity).At Hvanneyri at least, based on observations ofcolour-marked individuals, it is known that geesethat specialise on hayfield feeding do take to Carexlyngbyei meadows and E. angustifolium wetlandsat certain periods during spring staging. Whetherthis is due to depletion of the grassland resourceor improvement in the quality and/or availabil-ity of these natural foods is a subject of continu-ing investigation.

4.6 Conclusions & discussion

Greenland White-fronted Geese arriving in Ice-

land after the 1999 spring migration from Irelandwere on average 277 g (females) and 327 g (males)lighter than mean departure mass in Ireland. As-suming these mean values represent the real costsof flight over the distance involved, this is lessthan predicted, based on the aerodynamic pre-dictions. Studies at one of the most heavily usedspring staging areas at Hvanneyri in western Ice-land show rapid accumulation of body storesduring the stopover period. Based on a caughtsample and the use of field scores of abdominalprofiles converted to mass, the geese increasedbody mass by at least 30g and 25 g per day dur-ing the mean 15-day staging period there. Thetotal increase in body mass at this time wasslightly less than that over the mid-December tomid-April period on the winter grounds. As inthe case of the pre-migration period in Ireland, itremains to be demonstrated precisely what thisincrease in body mass equates to in terms of bodyconstituents. Although there was some evidencethat geese fed on adjacent wetlands, most of theincrease observed in this study was sustained onthe new green growth of cultivated grasslands.The three most common grass species showeddifferences in profitability because of leaf densi-ties and nutritional quality, which affected ratesof intake and hence accumulation of stores (Nye-gaard et al. 2001). Individual geese show differ-ent patterns of exploitation of the three grass spe-cies. Therefore, there is the potential for densityeffects and social status to play a role in deter-mining differential rates of individual nutrientacquisition on the staging areas, which could af-fect fitness. Because much of this rapid rate ofbody store accumulation is linked to green aboveground plant production, it is therefore likely tobe highly temperature dependent and likely tovary considerably with season. There is a need toassess whether there are differences in the ratesof body mass accumulation between the birdsfeeding on traditional bog (mainly Eriophorumangustifolium) and sedge-meadow (mainly Carexlyngbyei) habitats and those studied on farmland.Furthermore, given the unusually large field sizeat Hvanneyri and the relative lack of disturbance,it is important to contrast the relative energeticcosts and gains to a bird staging at this site ver-sus other farms elsewhere in the staging rangewhere disturbance rates are higher. This rapid rateof body store accumulation clearly makes thisbrief stop-over period more critical, in terms ofbalancing costs and gains, than other periods ofthe life cycle, and we need an adequate under-standing of what factors affect nutrient acquisi-

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tion during this critical time. All these factors needto be investigated and the results synthesised intoa full appraisal of the conservation needs of thepopulation. There remains a need to establish thesimultaneous staging distribution of Greenland

White-fronted Geese in the lowlands of Icelandin order to establish the basis for a network ofprotected and sympathetically managed sitesduring this critical period.

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of dietary fat and protein in order to attempt re-production at all.

As more studies have been carried out, it has be-come more apparent that few arctic nesting goosepopulations were truly capital breeders, in thesense that all reproductive material invested inclutches were derived from stores accumulatedby the female in areas remote from the breedingareas. It is now widely recognised that many pop-ulations exploit spring staging areas close to, butnot necessarily at, ultimate breeding sites andhence have the potential to supplement storesafter the main spring migration and prior to firstegg date. Raveling (1978) was amongst the firstto recognise that many species of northern or arc-tic-nesting goose regularly nested 10-13 days af-ter arrival on breeding areas, the period requiredfor rapid yolk development. This enables the fe-male goose to modify her timing of first egg dateand the investment in her clutch based on exter-nal (e.g. weather, nest site availability, e.g. Carriereet al. 1999) and internal conditions (e.g. extent ofstores, see Ganter & Cooke 1996).

It has since become clear that White-frontedGoose populations in particular rely upon pre-nesting feeding on the nesting grounds to sup-plement stores for investment in reproduction(Ely & Raveling 1989, Budeau et al. 1991). Otherspecies show the same response (e.g. the LesserSnow Goose, Ganter & Cooke 1996) including thevery high arctic Greater Snow Goose Anser caeru-lescens atlanticus, thought originally to breed soonafter arrival on the nesting areas (Choiniére &Gauthier 1995).

5.2 Mechanisms for recouping bodystores on the breeding grounds

Amongst the first studies to demonstrate pro-longed pre-nesting feeding on the breedinggrounds was that of the Greenland White-frontedGoose (MS1), where it was evident that geese fedlocally for the period of at least 10 days betweenthe first arrivals and the onset of breeding. Geesefed on the highly nutritious roots and stolons ofPuccinellia deschampsioides, bulbils of Triglochin pa-lustre and the lower stem of Eriophorum angustifo-lium and Carex spp., excavated from low altitude

5 Pre-nesting feeding

5.1 Introduction

Lack (1968) was the first to suggest that layingdates, clutch size and chick growth rates were co-adapted in birds to ensure maximum fitness. Lay-ing date is important, since in most studied goosepopulations, goslings hatching earlier have ahigher probability of survival and recruitmentthan those hatching later (e.g. Cooke et al. 1984,Warren 1990). Female geese in good body condi-tion generally lay larger clutches and fledge moreyoung than females in poorer condition (Ankney& MacInnes 1978, Ebbinge et al. 1982, Ebbinge1989, Prop & Deerenberg 1991, Johnson & Sibly1993, Warren 1994, Ebbinge & Spaans 1995).Hence, there is considerable evidence to supportthe idea that the ability of a female to accumulatenutrient stores at the earliest stage prior to theonset of breeding has a considerable influence onher ability to reproduce successfully in a givenyear.

For many years, it was considered that most arc-tic nesting geese built up stores on the winteringgrounds, supplementing body condition at oneor more staging area on spring migration beforethey reached the breeding areas. In the 1970s, theweight of evidence suggested that most arcticnesting geese bred immediately on arrival, or veryshortly after arrival, on their northern breedingareas (generally as soon as nest sites were freedfrom snow cover). Therefore, it was naturally as-sumed that the internal nutrient stores remain-ing on arrival to the nesting grounds were of con-siderable importance in determining reproduc-tive success (Barry 1962, Ryder 1970, Newton1977, Ankney & MacInnes 1978). However, it hasalways been apparent that any supplement to thereserves of a female goose on arrival at the breed-ing grounds will maintain or improve her gen-eral nutrient status and increase her chances ofreproductive success, as long as delay of first eggdate after arrival carries no cost. Theoretical con-siderations suggested that, for the Lesser SnowGoose Anser caerulescens caerulescens at least, thefat stores available on arrival were only sufficientto account for 46-70% of the lipid and 14-55% ofthe protein requirements for clutches of 3-6 eggs(Meijer & Drent 1999). From this standpoint, fe-male geese arriving at the breeding grounds haveto supplement stores with substantial amounts

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44

sandy substrates which were the first to thaw(MS1, Madsen & Fox 1981, Glahder 1999). Thesestorage organs, relatively rich in carbohydratesand protein, were available to foraging geese longbefore the onset of green above ground primaryproduction.

Once growth of such cyperacean plants starts,there is a rapid decline in absolute and relativequantities of storage polysaccharides and sugars(Shaver & Billings 1976) as well as nitrogen andphosphorous (specifically in E. angustifolium, Cha-pin et al. 1975). Hence, Greenland White-frontedGeese need to exploit this food resource immedi-ately the thaw enables its extraction from thesubstrate, but before growth starts and qualityrapidly declines. Climate change and the timingof migration therefore could have considerableimplications for the ability of geese to exploit sub-terranean plant storage organs during the pre-nesting period (and potentially at other times ofyears also) as patterns of spring thaw becomemodified. Geese arriving too early are unable toextract plants from a frozen substrate, those ar-riving too late encounter food of diminished anddeclining quality.

With almost continuous daylight and the protec-tion of their attendant gander, female geese fedfor 68-82% of the 24 hour period on these highquality foods for 10-19 days prior to clutch initia-tion (MS1, Fox & Madsen 1981, Glahder 1999).The period required for rapid oocyte develop-ment in Alaskan White-fronted Geese A.a.frontalisis considered to be 11-14 days (Ely 1979). Hence,arriving geese are not only in a position poten-tially to modify first egg dates given arrival con-ditions, but also to accumulate substantial storesduring this prelude to breeding.

5.3 Potential effects of differentialstaging within West Greenland

Based on studies undertaken in the southern partof the breeding range, satellite telemetry (MS20),observations of collared birds and other observa-tions all suggest that arriving pairs tended to con-gregate in localised rich feeding areas which arethe first to thaw (MS1, Glahder 1999). At suchsites, there was an initial concentrated exploita-tion of feeding resources, where females fed formaximum uninterrupted periods and malesgained some extra feeding time by associationwith groups of birds. Gradually, however, after

some 7 days, pairs split up and fed increasinglyaway from other birds, ultimately dispersing fromthe feeding aggregations close to ultimate nestsites, but still feeding on plant storage organs(MS20, Glahder 1999). In these situations, femalesincreased their abdominal profile index from amedian score of 1.5 to 2.5 between arrival on 4May and 19 May, males increased from 1.0-2.0over the same period (Glahder 1999). If the con-version factor determined from correlation of APIand body mass in Iceland holds for the breedinggrounds, this would represent an increase of 228g and 285 g of body mass respectively prior tofirst egg date. Some of the increase in API amongstfemales will correspond to the increase in the sizeand extent of the ovaries and reproductive appa-ratus, hence in this case it is unlikely that all theincrease in indices represents fat accumulation.Nevertheless, this field score supports the obser-vation that this opportunity for pre-nesting feed-ing provided an important period of recupera-tion of used body stores.

Observations of collared birds moving withinwest Greenland in spring 1984 (MS3) showedgeese may arrive and stage in one area and con-tinue elsewhere for the remainder of the summer.Based upon the behaviour of the satellite birds,in 1997, 1998 and 1999, geese arrived in westGreenland between 3 and 17 May and staged atarrival sites between Kangerlussuaq (66º30’N)and northern Disko Bugt (69º50’N). Geese con-tinued to their ultimate summer areas after aninitial staging period of 9 days in 1998, but 16 daysin 1999. One of the geese staged in the central partof the range before continuing to its summeringarea on Svartenhuk Peninsula in 1998, and simi-lar patterns were witnessed in 1999, when theprolonged snow cover meant potential feedingand nesting areas in the north of the range wereinaccessible well into June (MS20, MS23). It wouldtherefore seem that in the favoured breeding habi-tat around Kangerlussuaq (66º30’N) and furthernorth, the generally snow-free lowland wetlandsoffer a food resource to staging geese that breedlocally and others that move northwards withinthe summering range (MS1, MS2, MS3, MS20,Glahder 1999, Glahder et al. submitted). It mightbe expected that these local breeding birds haveaccess to earliest sources of food. However, as thepopulation has expanded, so these birds will havefaced increasing competition from the expansionin their own numbers and of those breeding fur-ther north that use the same spring staging areas.Glahder (1999) showed by combining satellite

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imagery and searches in helicopters, that snow-free areas in west Greenland with suitable veg-etation for staging White-fronted Geese were lim-ited (c.28 important areas, with 8 supporting over75% of all staging geese). Hence, there may beanother density-dependent mechanism (partlydependent upon the pattern of thaw in eachspring up the west coast of Greenland) which mayrestrict the ability of an individual to recoup itsstores in readiness for investment in reproduc-tion after the costs of migration from Iceland.

In seasons with a late thaw, geese staging in theregion of 66-69ºN but breeding further north facetwo alternatives. After initial refuelling they canmove northwards into (possibly) unknown con-ditions or remain further south amongst higherdensities of local breeders. In 1999, the thaw northof 69ºN was greatly delayed. Geese flying north-wards from staging areas would have encoun-tered low temperatures and complete snow cover,resulting in lack of access to food and high ther-moregulatory costs. In such a year, the northernsummering portion of the population would beexpected to breed with much lower success ratethan those in the south, and this was certainlythe case in 1999. The geese wintering at Islay(thought mainly to nest between 66 and 69ºN)returned in autumn 1999 with 10.5% young (abelow average production of young) but thosewintering at Wexford (thought to summer largelynorth of 69ºN) had the lowest level of productionon record (5.5% young). It could be expected that,in late springs when snow reduces the availabil-ity of feeding sites throughout west Greenland,competition for limited resources in the immedi-ate arrival period between 66-69ºN could poten-tially result in a general reduction in breedingsuccess in the population as a whole. Since nest-ing densities are still so low, and breeding habi-tat not obviously limited, it seems possible thatspring staging habitat could be a factor restrict-ing females from achieving breeding condition.This could be one limit to reproduction that wouldoperate well before any density threshold isreached where nesting habitat per se restricts thenumber of pairs attempting to nest. It is rare thatcold conditions prevail in the southern part of thebreeding range and not in the north, so a furtherprediction may be that, despite highest breedingdensities in the region of 66-69ºN, the effect islikely to be increasingly manifest amongst thebirds breeding in the north of the range.

5.4 Conclusions and discussion

We still know little about how Greenland White-fronted Geese acquire the resources to invest inreproduction on the nesting grounds after arrivalfrom Iceland. Much more research is needed todetermine the precise body condition of geesenewly arrived from Iceland and the consequencesof pre-nesting feeding and its contribution to asuccessful reproductive outcome. Arrival weightsconfirm that geese lose more weight (adult malesc. 550 g and adult females c. 330 g based on ar-rival API converted to mass from Glahder 1999)on the 1,500 km passage from Iceland than overthe same distance to Iceland from Ireland. How-ever, this difference is in line with prediction giventhe need to climb up over 2,800 m to traverse theGreenland Ice Cap along the trajectory taken bysatellite tagged individuals. There is a clear needto establish the precise mechanical costs of theflight over the Ice cap. We know birds congre-gate in favoured pre-nesting staging areas to re-coup stores immediately on arrival. During thistime, body mass (as calculated from changes inabdominal profile indices) increased at a similarrapid rate to that in Iceland in spring. Femalegeese, protected by attendant ganders, were ableto exploit a rich feeding resource in the form ofunderground storage organs of plants duringperiods of uninterrupted foraging. Male were alsoable to increase body mass at a similar rate dur-ing this time due perhaps to daylight extendingto 22 hours. Nest densities are generally low andnesting habitat apparently unlimited (see chap-ter 6). It therefore seems more likely that foodsupplies available at spring staging areas in thecentral part of the breeding range could limit theaccumulation of stores to support reproductionrather than any resource associated with the nest-ing sites themselves. Because it appears that asubstantial proportion of the entire populationstages between 66 and 69º N, given a finite feed-ing resource available, increasing goose densityat these staging areas may increasingly limit thenumber of geese attaining a level of body condi-tion sufficient to permit successful breeding. It ispredicted that the northern segment of the breed-ing population will not only face delayed timingof breeding by virtue of their nesting latitude andincreasingly lower summer temperatures pre-dicted from global climate change, but also theeffects of greater goose densities on the southernspring staging areas.

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6.1 Breeding distribution and nest sites

The breeding distribution and biology of theGreenland White-fronted Goose has not been es-pecially well described. The population is knownto nest in low arctic tundra areas between 64º and74º with greatest densities found between 66º and68º N (Salomonsen 1950, Best & Higgs 1990, MS23,MS24). Nesting densities are generally lower thanreported for other populations (<0.5 km-2, maxi-mum 0.28 km-2, MS5, MS23, compared with 0.4-30 km-2 in North America, MS5). There are nosigns of territorial behaviour amongst studiedbirds, nesting pairs being widely dispersed as aresult of the character of the available habitat(Stroud 1981a, MS24). First egg dates vary withseason and latitude, but generally fall in the lastweek of May, being 20-28 May in Sarqaqdalen(70º06'N, Fencker 1950), 19 May - 17 June inEqalummiut Nunaat (67º30'N, MS5). Nest site al-titude in Eqalummiut Nunaat was influenced byavailability of forage, determined by extent ofsnow cover and the phenology of the thaw. In1984, a very late spring thaw commenced rapidlyon 2 June when a warm föhn wind spectacularlythawed snow at all altitudes simultaneously. Thiswas in considerable contrast to 1979 when therewas little snow cover, but the thaw of the substrateprogressed slowly up an altitudinal gradient. In1979, nesting occurred early (mean clutch initia-tion 22 May 15 days after arrival, range 19-27 May)mostly at low altitude (below 300 m). In 1984,nesting occurred later (mean 11 June, 34 days af-ter arrival, range 6-17 June) and more often above400 m (MS1, Stroud 1981a, MS3, MS5). Nest sitesare extremely hard to characterise, being distrib-uted between sea level and 700 m altitude, butwere predominantly on 1) slopes above marshes,2) on or adjacent to marshes and 3) amongst hum-mocks adjacent to lakes (Stroud 1981a, MS5).Nests were almost exclusively near (invariablyoverlooking) Eriophorum angustifolium dominatedmarshes that in most cases formed the feedingarea of the loosely attendant gander and the fe-male during her recesses from incubation (Mad-sen & Fox 1981, Stroud 1981b, 1982, MS5). Nestsites were generally in the hollow top of a hum-mock, or tucked between hummocks. There wereno signs that nest site availability, access to feed-ing areas used during nesting, or breeding habi-

tat in general, were in any way likely to limit thenumbers of birds nesting at that time.

6.2 Incubation

Incubation lasts 25-27 days, carried out by femalesonly. Attendant ganders feed on nearby marshes,both birds showed strong diurnal rhythms inalertness, feeding and roosting (Stroud 1981b,1982, MS5). In 1979, the incubating female spentmost time vigilant during the middle part of theday, sleeping in the early morning. In 1984, thefemale slept at midday and was most alert in theearly morning. In 1979, four out of seven activelocated nests were unsuccessful and ultimatelypredated by Raven Corvus corax and/or ArcticFoxes Alopex lagopus (Fowles 1981). Foxes pre-dated five of the six nests located in 1984, althoughsuch a high predation rate could relate to the pres-ence of human observers (MS5). It is therefore notclear if these predation rates were in anyway typi-cal of situations without human observers. Itshould be noted, however, that in spring, birdseggs (especially those of geese) comprised a sig-nificant proportion of the Arctic Fox diet, in theabsence of other abundant prey items at that time(Birks & Penford 1990). In 1984, foxes were ob-served marking the positions of incubating White-fronted Geese on nests with scat marks, butseemed hesitant to attack sitting females, perhapsbecause of the risk of physical attack to the foxitself. Hence, the nest attentiveness of the incu-bating pair could play a critical role in determin-ing predation rates. Nest defence by a female,joined by her mate from his nearby feeding marshcould see off a fox, but a nest where an absentfemale is feeding on a distant wetland could of-fer a fox an easy source of food. Among NorthAmerican A. a. frontalis, groups of White-frontedGeese have been seen at nest sites and have joinedin attacking foxes at nest sites known not to betheir own (MS12). Such direct contributions tonest defence have not yet been reported fromGreenland.

All forms of clutch defence necessitate the maxi-mum attendance of the female at the nest, andhere again, there appears a possibility for a con-dition-mediated impact on reproductive output.

6 Reproduction

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A female with poor fat stores/reserves to main-tain her through incubation will need to spendmore time in feeding recesses away from the nestmore often than one with greater fuel reserves.Recesses in 1979 lasted an average of 24 minutes,the majority between 19.00 and 01.00 hrs; on 20June, the female left the nest twice in 24 hoursbut did not leave the nest again until 22 June whenthe clutch hatched (Stroud 1981b). Daily recessperiod increased from less than 20 minutes perday to 80 minutes as incubation progressed(Stroud 1981b), but the daily time spent incubat-ing was still high (98.8%). The female would leaveand fly towards the male, who would join herwithin seconds, the two birds flying to the feed-ing area. The male would stand alert close by thefemale whilst she drank and fed intensively; feed-ing was followed by bout of washing and preen-ing before returning by a direct flight to the nestsite. The male would stand within 20 m of thenest for the next 10-15 minutes before flying backto the marsh. The female spent some 20 minutesadjusting the nest, rolling the eggs and preeningbefore settling to incubation (Stroud 1981b). Thedaily time spent incubating was high comparedto Pacific Whitefronts A. a. frontalis (97.3%, Ely1979) and Pink-footed Geese (96.2%, Inglis 1977),but less than Emperor Geese A. canagius (99.5%,Thompson & Raveling, 1987, Thompson in MS5).This may perhaps imply a greater reliance uponbody stores to support the female through incu-bation than in other species, which supplementendogenous reserves by longer daily feeding re-cesses.

On hatching, young broods were escorted awayfrom the nest site to feed on wetlands andmarshes. In 1979, when nests were generally atlow altitude, this involved substantial movementof broods from lowland areas up onto the pla-teau lakes, at distances of up to 5 km and 3-400 muphill (MS5). In 1984, broods were hatched athigher elevations and did not move so far to nurs-ery areas (MS5). Although there are no specificdata on the relative predation rates in the twoyears, the distance over which parents must leadbroods across an open terrestrial landscape fromnest site to brood rearing habitats could affect theprobability that newly hatched young fall preyto Arctic Fox and Raven.

6.3 Fledging to hatching

Mean brood size fell from 3.70 (n=10) in late July

to 3.46 (n=5) by fledging in early August in 1979and from 4.25 (n=12) to 3.65 (n=20) in 1984. Par-ents were highly attentive to goslings at all times,while the goslings concentrated on feeding. Par-ents were observed brooding on a regular basisup to c.14 days after hatching, especially early on,for between 2 and 45 minutes per day, especiallyif the weather was cold or wet (Madsen 1981).Goslings were observed to run and seek shelterunder parents in the first few days after hatchwhen a Raven flew over, but when larger, theywould take to the safety of open water like theirparents. Parents that nested at mid-altitude in1979 immediately escorted their offspring up ontothe plateau one or two days after hatching. In1984, when the nests were constructed at higherelevations, broods had shorter journeys to get tothe ultimate brood rearing nursery areas aboutthe edge of plateau lakes. During brood rearing,parents fed for 35% of the time (42% amongst fe-males, 26% amongst males), goslings for an aver-age of 62% of the time, although the proportionof time spent feeding decreased gradually dur-ing the period to fledging (Madsen 1981). Onegosling was observed for 3 hours without everadopting the extreme head up posture typical ofalertness behaviour. Parents with large broodsspent proportionally more time vigilant than didparents of small broods or single goslings (Mad-sen 1981).

Non-breeders, which often moulted on the samelakes as breeders, were much less alert (althoughthey associated in larger groups) and fed less thanparents with young, which preened and restedless than the non-breeders. Non-breeders werenot tolerated as close to broods as were other fami-lies (mean inter-distances 22m and 10 m respec-tively) and flying non-breeders were driven awayfrom brood rearing areas by the parents. Attacksby breeders were more frequent on non-breedergroups than other broods and the attacking par-ents always won agonistic interactions even if thenon-breeding groups were larger than the familyflocks (Madsen 1981). On three different occa-sions, single associating non-breeders were tol-erated at very close proximity to broods (Madsen1981).

There are no currently available data relating tothe condition of the adult female following incu-bation. As discussed later (chapter 9, Figure 9.4),following incubation, the female has invested inher clutch and incubated for an extended periodcharacterised by very short feeding recesses. It is

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predicted that at the end of this period of inten-sive investment, her body mass may well reachthe lowest levels in the annual cycle (see Owen1980, Figure 41). Potentially she will have de-pleted both stores (accumulated in advance ofsuch investment) and reserves (body constituentsnot normally utilised to balance nutrient or en-ergy budgets) during the period on the nest. Hersurvival is therefore highly likely to be influencedby her ability to regain adequate body conditionin readiness for the wing moult. Since broods maybe reared in habitats which offer the greatestabundance of the most suitable dietary items forgosling growth (for example high protein andenergy content, low fibre but very small bite size),gosling nursery areas may not offer the best for-aging opportunities to females to make goodlosses during incubation. Generally, this periodin west Greenland is one of rapid plant growth,with locally abundant food resources and it isunlikely that there is a limit on the ability of broodfemales to make good such losses. Furthermore,there are no general indications amongst collaredindividuals of a high frequency of occurrence ofwidowed males returning to the winteringgrounds with broods. Nevertheless, the ability ofbrood females to re-establish body condition froma particularly low level would repay study at thiscritical time.

6.4 Fledging to maturity

The period from fledging until departure fromthe summering areas has not yet been studied inany detail. Salomonsen (1950, 1967) describedgeese gathering into flocks and moving to lakesalong the ice cap margin in continental westGreenland. Certainly geese are known to resortto heath areas in the interior at this time in thevicinity of Kangerlussuaq to feed intensively onberries prior to autumn migration (A. Reenberg,pers. comm.). This is an urgent research priority,since the accumulation of stores for the autumnmigration to Iceland is a critical period in the an-nual life cycle about which nothing is known.

One pair observed throughout incubation in 1979raised five goslings from six eggs of which foursurvived to reach Kintyre in Scotland (one gos-ling was shot in Iceland). In 1984, another ob-served pair raised six young from six eggs andalthough all were ringed, none have been subse-quently recorded in Ireland or Britain. Meanbrood size post fledging in Greenland in 1979 and

1984 fell from 3.46 and 3.65 respectively to 2.84on the wintering areas in both years (based onmean brood size on Islay in both years in Novem-ber, n = 68 and n = 80 for 1979 and 1984, MS5).Overall, 7% of goslings ringed in Greenland since1979 have been shot and reported in Iceland ontheir first autumn passage to the winteringgrounds. Annual survival of birds in their firstyear (i.e from first to second winter 59.6%, 95%confidence limits 29.8%-89.5%) was significantlyless than that of older birds (72.4%, 58.3-86.6%C.L. for the years 1984-1989, MS10), despite closeassociation with parents in the first year (MS11).More recent analysis using a combination of ring-ing recoveries and capture-recapture analysisusing resightings of collared birds gives a similarrelationship (first-year weighted mean survival67.8%, 63.2-72.0% C.L. versus 78.5%, 76.2-80.5%C.L. for adults, M. Frederiksen & A.D. Fox un-published). Mean age at first pairing was 2.46years (± 0.08 SE), age at first successful breeding3.15 (± 0.17 SE) with no significant differencesbetween the sexes (MS8).

6.5 Overall breeding success

The only regular long-term measure of breedingsuccess comes from the wintering grounds, wherethe determination of mean family brood size andthe proportions of young in the wintering flockshas been a regular feature of the monitoring pro-gramme for the population since 1982 (MS14, Foxet al. 1999). For some resorts, principally Islay andWexford, the main Scottish and Irish winteringsites, these data are available since at least 1968.These indices of production underestimate trueproduction. This is because they represent thenumbers of young in the population after theimpacts of autumn migration mortality. This in-cludes hunting in Iceland, where it is known thatjuvenile birds are over-represented in the hunt-ing bag of some 3,000 birds shot there annuallyin autumn (Wildlife Management Institute 1999,A. Sigfusson pers. comm.).

The annual production of young in the Green-land White-fronted Goose is positively correlatedwith average June temperatures (Zöckler & Ly-senko 2000). In 1992 (a late cold spring, with lessthan 10% young in the following autumn), 24 fam-ilies were encountered during 2,538 km of flowntransects counting geese on the breeding grounds.This compares with 83 during 3,298 km of aerialsurvey in 1995 (a mild spring followed by a warm

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summer, with 20% young in Scotland – i.e. highproduction, Glahder 1999). However, this may notalways be the case (e.g. production of similarnumbers of young in the same study area in 1979and 1984 despite a difference of almost a monthin the timing of the spring thaw MS5). Further-more, Greenland White-fronted Geese nest overan unusually broad range of latitudes so that, evenwithin seasons, weather conditions in the south-ern parts of the range may differ widely fromthose in the north. Densities of families on thebreeding grounds vary with the general levels ofbreeding success. The recent breeding survey of1999 (a very late spring compared with most re-cent years) showed that by early June, conditions

on the breeding areas were good in the south ofthe range, but that deep snow conditions pre-vailed from Disko Bay northwards (MS23). Theconsequence may well have been that breedingbirds in the north of the range abandoned at-tempts to nest altogether, since at Wexford (wherethe majority of birds originate from the north ofthe breeding range) geese returned with the low-est ever recorded proportion of young (chapter5).

The proportions of young in the autumn popula-tion are generally lower than in most other pop-ulations of White-fronted Geese and other greygeese in the Western Palearctic (see Table 6.1). At

PopulationMean % juveniles

(time period for sample) Mean brood size Source

Taiga Bean GooseAnser fabalis fabalis

28.7(1981-1989)

- Madsen et al. (1999)

Tundra Bean GooseAnser fabalis rossicus

25.0(1970-1994)

van Impe (1996)

Iceland Pink-footed GooseAnser brachyrhynchus

17.9(1970-1995)

Madsen et al. (1999)

Svalbard Pink-footed GooseAnser brachyrhynchus

16.9(1980-1995)

Madsen et al. (1999)

Iceland Greylag GooseAnser anser

17.7(1970-1995)

Madsen et al. (1999)

Scottish Greylag GooseAnser anser

26.8(1986-1997)

Madsen et al. (1999)

North AmericanWhite-fronted GeeseAnser albifrons

Eastern Mid-Continent 33.3(1979-1999)

US Fish & Wildlife Service (1999)

Western Mid-Continent 31.2(1979-1999)

US Fish & Wildlife Service (1999)

Pacific 33.1(1961-1999)

US Fish & Wildlife Service (1999)

Tule 26.2(1986-1999)

US Fish & Wildlife Service (1999)

Western PalearcticWhite-fronted GeeseAnser albifrons

Zeeland, Netherlands 29.0(1970-1994)

van Impe (1996)

Greenland White-fronted Geese A. a. flavirostris

Wexford 16.3(1968-1999)

this study

Islay 14.9(1968-1999)

2.10

2.09

2.03

2.24

3.68

1.67

2.07

2.18

2.5

3.41

3.17 this study

Table 6.1. Productivity data for Western Palearctic grey geese Anser spp. and for other populations of thecircumpolar White-fronted Geese Anser albifrons.

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Wexford, the mean proportion of young for theyears 1968-1999 inclusive was 16.3% (± 0.986 SE;range 5.5% in 1999 to 32.5% in 1969 data courtesyOscar Merne, Dave Norriss, Alyn Walsh, Dúchas,The Heritage Service, National Parks & Wildlife,Ireland, Figure 6.1). On Islay for the years 1968-1999 inclusive it was 14.9% (± 0.945 SE; range 6.7%in 1992 to 27.3% in 1985 (data courtesy MalcolmOgilvie, Greenland White-fronted Goose Study,Wildfowl and Wetlands Trust, Scottish NaturalHeritage, Figure 6.1). Until recently, flocks atWexford contained consistently higher propor-tions of young than at other resorts, and the sameis true of the Islay birds compared to flocks in the

rest of Britain (Pettifor et al. 1999). Overall, theannual patterns of breeding success are highlycorrelated between winter resorts (e.g. Figure 6.2).Poor seasons are associated with late spring thawwhere thick snow cover in northern areas leadsto abandonment of breeding (e.g. 5.5% at Wex-ford in 1999) or early snow in July which mayaffect gosling survival (e.g. 6.4% at Wexford in1996). The relatively low percentage of young,returning in relatively large family units (see com-parisons in Table 6.1 above), means that far fewerGreenland White-fronted Geese of potentiallyreproductive age return with young to the win-ter areas than is the case in other Whitefront pop-ulations. Whether this is the result of geese at-tempting to breed but failing, or simply not at-tempting to breed is central to understanding whyrecruitment is relatively low in this population.

There has been a significant decline in the overallbreeding success amongst the population winter-ing at Wexford since protection, although therewas no significant trend on Islay (see Figure 6.1).If it is assumed that birds can breed in their sec-ond summer (although there is little evidence thatmany do) there has been a significant decline inthe proportions of those birds of potential breed-ing age which return to the wintering groundswith young at both major resorts (Figure 6.3).Hence, amongst both of the two major winteringaggregations (Wexford and Islay), there has beena decline in the proportion of potentially fecundbirds that reproduce successfully since 1982. Pro-

0

10

20

30

40

0 10 20 30 40

Percentage young at Wexford

Per

cent

age

youn

g on

Isla

y

pre-protection post-protection

Figure 6.2. Patterns of annual breeding success (ex-pressed as percentage juveniles in the winter flocks)at Wexford and on Islay for the period 1968-1999. Thediagonal line signifies the line of equal production.

Figure 6.1. Annual breeding success of GreenlandWhite-fronted Goose expressed as the proportion ofjuvenile birds in the wintering flocks at Wexford andon Islay for the years 1962-1999. Vertical arrow indi-cates the point at which hunting on the winteringgrounds ceased (i.e. affecting both sites). Best fit leastsquares regression models are shown for both sites (asin following graph plots), the decline in proportion ofyoung at Wexford since protection is statistically sig-nificant, although the decrease was not statisticallysignificant for the trend on Islay4.

0

10

20

30

40

1960 1970 1980 1990 2000

Census year

Per

cent

age

of ju

veni

les

Wexford

Islay

Wexford

Islay

0

0.1

0.2

0.3

1960 1970 1980 1990 2000

Census year

Pro

port

ion

of p

oten

tial b

reed

ers

that

are

suc

cess

ful

Wexford

Islay

Wexford

Islay

Figure 6.3. The proportion of potentially breeding adultfemales (assuming birds could potentially breed intheir second summer) amongst the wintering flockson Islay and Wexford that have returned annually withyoung during the period 1968-1999. The vertical ar-row indicates the point at which the population wasprotected from hunting on the wintering grounds (i.e.at both sites). There have been statistically significantdeclines in these proportions at both sites since pro-tection5.

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ductivity of other wintering flocks away fromthese two major resorts is generally lower. Be-cause these two sites have held 57-63% of theworld population in the last 3 years, this hasdoubtless contributed to the general reduction inthe rate of increase in the overall population. Sinceprotection, the absolute number of successfulbreeding pairs returning to the winter groundshas increased on Islay (although not significantly)and has declined significantly at Wexford (Fig-ure 6.4). The result is that the size of the combined

successful breeding population amongst 60% ofthe entire subspecies has remained remarkablysimilar (just under 1000 successful pairs in mostyears, excepting summers with cold weather con-ditions, Figure 9.3), despite the overall increasein the population as a whole. The consequencehas been a reduction in the number of young pro-duced annually per female of reproductively ac-tive age, although this decline is not statisticallysignificant on Islay (Figure 6.5).

Amongst the sample of marked individuals, therehas been a significant long-term decline in theproportion of ringed cohorts of young Wexfordbirds that survive and breed at least once (Figure6.6). There was also an increase in the mean ageof first breeding after 1988 amongst cohorts ofbirds marked as juveniles at Wexford in their firstwinter (Figure 6.7). Reductions again since 1992are partly due to surviving birds from these co-horts failing to recruit to the present time. Therehas been no apparent change in the age of firstpairing amongst these age classes during the pe-riod. This tends to suggest some density depend-ent mechanism may be operating at some stageof the life cycle. This increasingly precludes youngrecruits from entering the breeding class and re-duces the numbers of birds of potential breedingstatus attaining that status in any one year. Al-though interpretation of such data is limited be-cause of the delayed age of first breeding in thepopulation, it should be considered that onlyc.10% of birds collared as first winter birds sur-vive to their 6th winter. Any belated recruitment

0

0.2

0.4

0.6

0.8

1

1960 1970 1980 1990 2000

Census year

Num

ber

of y

oung

pro

duce

d pe

r po

tent

ially

bre

edin

g fe

mal

e

Wexford

Islay

Wexford

Islay

Figure 6.5. Annual production of young per potentiallybreeding female for the period 1968-1999 based ondeterminations on the wintering grounds at Wexfordand Islay. The vertical arrow indicates the point atwhich the population was protected from hunting onthe wintering grounds (i.e. at both sites). There hasbeen statistically significant decline in this measureamongst geese returning to Wexford since protection,but the decrease was not statistically significant forthe trend on Islay7.

0

5

25

20

15

10

1982 1984 1986 1988 1990 1992 1994 1996

Cohort year

% o

f age

cla

ss k

now

n to

bre

ed

Figure 6.6. The proportion of each age class of goslingscaptured and marked in their first winter at Wexfordand known to have survived to breed successfullysince ringing commenced in 1983. Note that there arestill several surviving birds from cohorts hatched since1992 that have yet to breed and could recruit in futureyears. The decline is significant, but without the co-horts 1992-1994 inclusive, the trend is not significant8.

Figure 6.4. The annual number of pairs of GreenlandWhite-fronted Goose returning to Wexford and Islaywith young from the breeding grounds during theyears 1968-1999. Estimates are based upon the num-bers of young divided by the mean brood size. Thevertical arrow indicates the point at which the popu-lation was protected from hunting on the winteringgrounds (i.e. at both sites). There has been statisticallysignificant decline in the number of successful pairsreturning to Wexford since protection, although therewas no statistically significant trend on Islay6.

0

200

400

600

800

1960 1970 1980 1990 2000

Census year

Num

ber

of s

ucce

ssfu

l pai

rs

Wexford

Islay

Wexford

Islay

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of survivors of cohorts from 1988 onwards (Fig-ure 6.7) will increase mean age at first breedingand make very little proportional difference to theproportions breeding shown in Figure 6.6.

Mean brood size amongst flavirostris has alwaysbeen relatively high compared to other White-fronted Goose races, varying between 2.4 and 4.2at both Wexford (mean 3.4 ± 0.07 SE) and Islay(mean 3.1 ± 0.07 SE) during the years 1968-1999.Mean brood size at Wexford was highly signifi-cantly correlated with proportion of young inwinter, but there was no such relationship on Is-lay. There was a tendency for larger broods withincreasing age of first breeding (MS8). This sug-gests that there could be some reproductive ben-efit to the individual from prolonged associationwith parents (in terms of production of young attheir first breeding attempt). There has been asudden increase in brood size amongst birds win-tering on Islay in very recent seasons, despite nochange in the observer or methods used to sam-ple this parameter there (Figure 6.8). This has re-sulted in the mean brood size on Islay exceedingthat at Wexford (generally always the converseuntil the mid-1990s, Figure 6.8). While in the 1970sand 1980s the productivity of the Wexford birdswas nearly always greater than that of Islay win-tering birds, in recent years this difference hasreduced, and Islay productivity has in severalrecent years exceeded that at Wexford. Evidencefor any density-dependent relationship for pro-ductivity was weak amongst the Scottish winter-ing flocks (Pettifor et al. 1999) and non-existent

amongst the Wexford wintering element of thepopulation.

6.6 What does limit reproduction in thispopulation?

We may be very encouraged that recent yearshave seen a huge increase in the basic descrip-tive knowledge relating to the breeding biologyand ecology of Greenland White-fronted Geese.However, from a conservation point of view, allthe descriptive information is useless if we areunable to identify and understand the processesinvolved. Direct comparisons with other White-fronted Goose races show that proportionallyfewer flavirostris of potential breeding age returnto the wintering areas with young. Yet when theydo breed, they return with more juvenile geeseper family than those of other races (see compari-sons in Table 6.1). The implication is that the re-productive potential of the population is lockedup in a small number of highly successful breed-ing pairs. The question therefore remains: whydo so few females of breeding age return withyoung? And why is this number presently declin-ing? Is it because of delayed pairing (and pro-longed parent offspring associations) comparedto other races (MS8, MS11)? Do offspring simplyassociate with parents and siblings because theycan contribute to the reproductive output of kinand accumulate reproductive knowledge duringa period when they have little prospect of breed-ing successfully? Or do they pair no later than

Figure 6.8. Mean annual brood size of GreenlandWhite-fronted Geese returning to the two major win-tering areas of Wexford and Islay. The vertical arrowindicates the point at which the population was pro-tected from hunting on the wintering grounds (i.e. atboth sites). The decline in brood size at Wexford since1983 is statistically significant, as is the significant in-crease on Islay9.

2

3

4

5

1960 1970 1980 1990 2000

Census year

Mea

n br

ood

size Wexford

Islay

Wexford

Islay

Figure 6.7. Mean age of first successful breeding (+ SE,determined by the return of an individual to the win-tering grounds with at least one gosling) of goslingscaptured and marked in their first winter at Wexfordsince ringing commenced in 1983. Note that there arestill several surviving birds from cohorts hatched since1992 that have yet to breed and could yet recruit infuture years, although these would only raise the meanage of first breeding for these latter cohorts.

0

1

2

3

4

5

6

7

8

1982 1984 1986 1988 1990 1992 1994 1996

Cohort year

Mea

n ag

e of

firs

t bre

edin

g

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other races, but density dependent processes re-strict the ability of young inexperienced birds tonest and incubate successfully? The increase inthe age of first breeding in very recent years hascontributed to the general decline in recruitmentamongst marked cohorts of known age birds since1984. Observations on the wintering groundsshow that Greenland White-fronted Geese havea rigid social dominance hierarchy, so that a ma-jor determinant of an individuals’ access to bestfeeding opportunities is the size of group withwhich it is associated (Boyd 1953). A young pair,abandoning the ties with parent-sibling groups(which may number up to 15 individuals in size)falls from a high-ranking group to a two-mem-ber group, with all the consequences for access tofood and other resources that this behaviouralchange entails. Hence, the first step towards areproductive attempt, that of obtaining a mateand accumulating appropriate stores for invest-ment in successful reproduction, may carry a veryheavy initial cost. The benefits of membership oflarge extended family units are found on the stag-ing areas as well. In spring, family groupingsmaintained on the wintering grounds are per-petuated at staging areas in Iceland (MS27).Hence, at a number of stages in the life cycle, thedecision to leave a family, form a pair and investin a reproductive attempt may result in loss ofaccess to best feeding opportunities at a numberof points in the non-breeding periods of the an-nual cycle.

On the breeding areas, too, there may be advan-tages to existing parents of extended parent-off-spring relationships. In another race of White-fronted Geese, central Canadian arctic frontalisyoung of previous years have been seen contrib-ute to pre-nesting feeding alertness of potentiallybreeding pairs, and to remain in the vicinity ofnest sites to assist with nest defence (MS12). Inthe absence of such 'helpers', new breeders mayrisk higher predation rates and hence impairedreproductive output for reasons other than expe-rience. In terms of securing resources for the an-nual cycle of overwinter survival, spring migra-tion and investment in reproduction, there wouldseem every advantage to remain with a group ofkin, even for part of the year. However, as far aswe know, this does not happen. Young birds leavefamily groups on pairing to embark upon a re-productive attempt as a lone pair. Hence, the lowreproductive output of this population may inpart relate to the behavioural consequences offlock structure, which creates a disincentive for

young birds to leave a large social group of re-lated birds and attempt to 'set up home alone' asa lone pair. In other words, the high resource costof leaving a family grouping favours delayedpairing relative to other races of the same spe-cies. Mature breeding pairs have the benefit ofexperience and the presence of associated off-spring “helpers” from previous seasons. In con-trast, inexperienced first time breeders (lackingassociates) are likely to fail in the early stages oftheir reproductive lives. Furthermore, there couldbe some advantages to offspring in extended as-sociation with parents in gaining knowledgeabout successful reproductive techniques. This issupported by the fact that brood size increaseswith age at first breeding (MS8).

Given the continued increase in the numbers ofgeese wintering on Islay and the decline at Wex-ford, it is tempting to speculate that these differ-ences in patterns of abundance are related to fac-tors affecting the birds on the wintering areas. Theextent of favoured feeding habitat has been re-duced at Wexford in recent years, which couldpotentially affect the condition of departing birdsand hence their reproductive success. There havebeen great changes in the extent and quality ofgrassland most favoured by the geese at WexfordSlobs in the last 14 years, and this has been re-flected in the habitat use by collared geese at thesite (Figure 6.9). Geese there increasingly use fod-der beet provided as a sacrificial crop for longer

0

10

20

30

40

50

60

70

80

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1984

1986

1988

1990

1992

1994

1996

1998

Year

Per

cent

age

habi

tat u

se

Reseeded grass

Stubble

Root crops

Winter cereal

Beans

Figure 6.9. Proportion of different major habitat typesused by wintering Greenland White-fronted Geesewintering at Wexford Slobs during the period 1984/85-1998/99. Data presented are based upon observa-tions of collared birds only, since habitat type is re-corded for every single field observation of these birds.There has been a significant decline in the use of grassand significant increase in the use of root crops (prin-cipally beet increasingly grown as a sacrificial crop forgoose use at the site)10.

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periods in each winter as the extent of suitablequality grass falls and tillage of former grasslandareas (to produce crops largely unattractive toWhite-fronts such as linseed and maize) has in-creased. These changes in habitat use may havehad nutritional consequences for the geese, whichaffect their propensity to breed, although there isno clear evidence of this from reduced API scoresat departure in very recent years (see Figure 3.3).

Flocks of Greenland White-fronted Geese winter-ing at other sites in the south of the range are alsoshowing the greatest declines in numbers in con-trast to those in the north (MS14). Perhaps globalclimate change, or agricultural changes have insome way increased grass growth, especially inspring, in such a way that the timing of the nutri-tional early stages of growth no longer coincideswith the pre-migratory fattening period of theWhite-fronts. Such arguments seem unlikely toprovide a full explanation for what happens tobirds 3,000 km away, given that the geese have 3weeks to accumulate stores and reserves very rap-idly in Iceland. Even after arrival in west Green-land, depending on the conditions encounteredthere, geese usually have a further period of 2-3weeks feeding prior to initiation of nesting there.

Since patterns of winter segregation shows somerelationship to those on the staging and breedingareas, it is equally, if not more likely that it is fac-tors operating in Iceland and Greenland that arein some way restricting nutrient acquisition andhence recruitment. One major factor likely to af-fect geese (assuming a finite and constant foodresource) is the increase in local bird density as aresult of the recent expansion in numbers. Priorto protection, the birds using Islay and Wexfordcombined would have contributed some 6,400non-breeding birds annually to the population asa whole. With the increase in overall numbers,the average number since 1982 has been 13,500non-breeders. There are consequently more thandouble the numbers of geese summering in westGreenland than in previous years, and to thesemust be added the increasing numbers of CanadaGeese colonising from North America. SomeWhite-fronts show signs of moult migrationnorthwards within Greenland, and the majorityof the moult migrant Canada Geese were in thenorthern part of the breeding range of the Green-land White-fronted Goose. Hence, it seems likelythat there may be increasing competition for foodresources in the northern part of the range. There,the thaw has always been later (and therefore

productivity more variable dependent uponweather). The additional numbers of moult mi-grant non-breeders of both species could, how-ever, have resulted in increased depletion of re-sources, perhaps at the cost of the number of suc-cessfully breeding birds in the area. To affect out-put, this density dependent effect would have tooperate at pre-breeding feeding sites, eitherthrough direct interference competition for a fi-nite resource or (in the case of food items takingmore than one year to recover from exploitation)through a reduction in the overall food stock. Suchan effect would be expected to be most manifestamongst the Wexford wintering birds, especiallyin seasons when the spring thaw was delayed, ashas been increasingly the case in recent years.Hence, the overall decline in reproductive out-put may represent the combined effect of increas-ing numbers of geese and the result of the gen-eral cooling of the climate in western Greenland.This cooling has been occurring since the 1990s(Rigor et al. 2000) and is predicted by the variousmodels of climate change to continue.

To distinguish between these two alternative ex-planations, we need to follow closely the behav-iour and nutritional status of individual birds atevery stage in their annual cycle. Althoughchanges in fecundity have been documented,their proximate and ultimate causes remain ob-scure. What is important is that the populationsize and reproductive output should continue tobe monitored in such a way that we can continueto follow the trends in population parameters andmake some predictions about the likely trajectoryof overall population size in the future. In thisrespect, it is important to understand factors af-fecting annual survival as well as fecundity, asubject considered in chapter 8.

6.7 Conclusions and discussion

Investment in reproduction in a long-lived ani-mal represents a trade off between the availabil-ity of current resources, the cost of the reproduc-tion attempt and the probability of surviving tobreed again in a future year. It seems reasonableto assume that female condition determines thelevel of effort invested in reproduction, up to thepoint where the effort threatens her own futuresurvival. In terms of initial investment, it appearsthat given the relatively long period of pre-nest-ing feeding in Greenland, clutch size decisionsmay be made by Whitefronts on the breeding ar-

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eas (see Raveling 1978, Ganter & Cooke 1996)based on their own internal condition and theprevailing environmental conditions. This wouldinvolve assessment by the females of their abilityto meet the nutritional demands of laying differ-ing numbers of eggs and incubating the clutchgiven available stores and the supplement possi-ble from exogenous food sources. Evidence is ac-cumulating to suggest that exogenous sourcessupply much, or perhaps all of the fat needed foregg formation (Choinière & Gauthier 1995, Ganter& Cooke 1996, Meijer & Drent 1999). Hence, ac-cess to adequate food resources prior to first eggdate may have a considerable impact on the abil-ity of a bird to reproduce successfully.

We know little about female condition and its po-tential to affect reproductive success (before, dur-ing and after nesting), so the accumulation ofknowledge relating to this parameter remains apriority. In particular, following body masschanges in particular individuals during the pe-riod from first arrival in west Greenland throughto the end of incubation would be highly desir-able. Tracking changes in body mass by captureand the use of balances under nests offers theopportunity to assess and contrast the potentialof different individuals to successfully investstores and reserves in reproductive attempts.Similarly, it is of great interest to understand moreabout how brood females recoup stores and re-serves exploited during the laying and incuba-tion period, a process about which we know noth-ing at present. Clearly behavioural adaptations(i.e. mechanisms resolving the conflict betweenself-maintenance and investment in brood pro-tection) and dietary selection are both potentiallyinvolved, but could differ between individuals.

Despite the recent expansion in total populationsize, the absolute numbers of successfully breed-ing pairs returning with young to the two majorwintering sites combined have been more or lessconstant, suggesting some density-dependentmechanism is operating on the breeding groundswhich restricts recruitment. Amongst known agemarked individuals at Wexford, the probabilityof recruitment has declined over time and themean age of first breeding has increased from c.3prior to 1988 to c.5 years of age in subsequentyears.

Although difficult to measure in an objective way,the extent of breeding habitat available through-

out the summer range does not appear limiting.Nevertheless, the extent of habitat available inspring for pre-nesting feeding as well as later inthe summer, are likely to vary with weather con-ditions, especially in the north. The Wexford geesebreed mainly in the north of the breeding range,and the recent declines in fecundity of birds win-tering at that site seem likely to be the result ofconditions these birds encounter on their pre-breeding and nesting areas. Their migration towest Greenland differs little in distance or routefrom the Scottish wintering element of the popu-lation that breed further south. They could expe-rience less access to energy-rich foods (such asbarley and potatoes) in western than in southernIceland, which could enable greater energy storesto be accumulated by predominantly Scottishbirds staging in these Iceland lowlands (MS4,MS19). However, if it is exogenous energy derivedon the breeding areas that represents a major de-terminant of clutch size or quality, early arrivalto staging areas in southern Iceland (MS19) wouldgive these birds an advantage over geese breed-ing further north. The latter would not only com-pete with local breeders in the staging areas ofcentral west Greenland but also then migratenorthwards within Greenland with a high prob-ability of encountering severe weather conditionson arrival at ultimate nesting grounds. As goosedensities have increased in recent years, it maybe that all potentially breeding White-frontedGeese are encountering more competition for lim-ited resources in spring, but the birds still need-ing to continue north face increased competitionfrom non-breeders. As there is no further habitatto the north of the current range into which toexpand, it might therefore be expected that geesebreeding in the north of the range show greaterdensity-dependent effects on the summering ar-eas than those nesting further south. There issome evidence that this is the case; on Islay, theproduction of young per potentially breeding fe-male has not declined significantly, the decline insuccessful breeding being compensated for tosome extent by increases in mean brood size invery recent years. Increased mean brood size im-plies (i) adequate stores to lay large clutches, (ii)to incubate these successfully and (iii) to raisegoslings to fledging. If the breeding range of theIslay-wintering birds has not changed, it is un-likely that their increased brood sizes have beenbrought about by change in habitat. Since theirbreeding area (mainly 66-69ºN) is the area withgreatest density of colonising breeding Canada

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Geese, it might be expected that inter-specific in-teractions in this area would reduce reproductiveoutput.

It may have been the case in the 1970s (prior tothe period of population expansion by restrictionof winter hunting) the northern breeders had anadvantage over southern breeders. Staging fur-ther south on the summer grounds gave the op-portunity to accumulate nutrient and energystores remote from breeding areas, but still timearrival to nesting areas to optimise food availabil-ity there. This seems to be reflected in greater pro-ductivity amongst Wexford compared to Islaybirds at that time (Figures 6.2 and 6.4). Subse-quently, conditions of greater population sizehave increased local feeding densities in springand substantially increased moult migrant non-breeder numbers using northern areas to regrowflight feathers. These changes in local density atkey stages of the life cycle could potentially haveturned the strategic advantage into an increasingdisadvantage, especially at a time when a seriesof late springs has constrained the overall avail-ability of early season food.

It seems likely that breeding habitat has notchanged in extent, but that the quantity (and pos-

sibly the quality) of the resources available to fe-males arriving in west Greenland have increased.Global climate models suggest there will be ashort term and moderate warming of the centralwest Greenland coastal strip, whilst summer tem-peratures further north will be expected to fall.While increases in total population size may re-duce overall access to finite food resources throughcompetition, best quality individuals able to de-fend rich spring feeding areas could rapidly gaincondition to invest in a clutch to be laid locally.Birds breeding further north face increased feed-ing competition, and poorer summer conditionslater in the season on their own pre-nesting andbreeding areas further north. Consequently, Wex-ford-wintering geese may be undergoing the verydeclines in fecundity predicted on the basis of cli-mate change by Zöckler & Lysenko (2000), whilstIslay-wintering birds enjoy the positive benefitsof this change. It would be interesting to analysethe historical meteorological archive to determinewhether the difference in fecundity of these twoelements of the population can be related toweather patterns in the north and south of therange. If not, there seem grounds for assessing inmore detail the alternative explanations for thesedifferences in breeding success in different ele-ments of the population.

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7.1 Introduction

Considering the annual cycle of birds in the con-text of periods of nutritional stress, the period ofreplacement of the body plumage represents onesuch stage. The maintenance of plumage has con-siderable consequences for the individual, not justin terms of flight and aerodynamic efficiency, butalso because feathers provide effective thermalinsulation and, in the case of waterbirds, buoy-ancy. The Anatidae have evolved a pattern of re-placement of feathers throughout the annual cy-cle, and indeed, ducks may have multipleplumages and moult throughout the year. Innorthern geese, replacement of feathers occursthroughout the annual cycle, except during thebreeding period (e.g. Gates et al. 1993), althoughit is the period of flightlessness during the post-breeding phase which has attracted most researchattention (Hohman et al. 1992).

In common with most of the Anatidae, and allnorthern-nesting geese, Greenland White-frontedGeese shed their flight feathers simultaneouslyand become flightless for a period of 3-4 weeks(Belman 1981). Flightlessness constrains feedingopportunities and denies flying as a means ofpredator escape, hence it seems highly likely thatselection will have reduced the flightless periodas much as food resources and predation riskwould permit. Whether the flightless period rep-resents a period of stress (i.e. where the nutrientdemands of a bird exceed the supply derived fromingestion, resulting in catabolism of body tissueto meet that demand, sensu Ankney 1979) hasbeen the subject of considerable debate (seeHohman et al. 1992). Hanson (1962) demonstratedthat captive Canada Geese, fed ad libidum through-out wing moult, lost weight. Ankney (1979)pointed out that goslings increase their bodyweight 20 fold, grow leg and breast muscles andossify a skeleton to almost adult size and grow afull set of body tail and flight feathers. Hence, heconsidered that it would be surprising if adultLesser Snow Geese could not meet the nutrientdemands of wing moult over the same time pe-riod. Nevertheless, Owen & Ogilvie (1979)showed significant declines in body mass withmoult stage in Barnacle Geese in Svalbardamongst adult males and yearling females. Gateset al. (1993) demonstrated significant declines in

lipid reserves during wing moult in breeding fe-males and non-breeding Canada Geese, suggest-ing that energy stores (i.e. nutrients accumulatedin advance of periods of demand, sensu van derMeer & Piersma 1994) may be built up in advanceof wing moult. Non-breeding Greylag GeeseAnser anser moulting on the Danish island ofSaltholm selected the most protein rich food avail-able (Fox et al. 1998) and showed modificationsto their nitrogen metabolism (Fox & Kahlert 1999),yet still lost 12-26% of their body weight (MS17).Subsequent dissection of birds obtained at thissite throughout wing moult has shown that mostof this involves use of extensive abdominal, me-senteric and sub-cutaneous fat deposits which arecompletely depleted by the time flight feathersare regrown (unpublished data). The study of vanEerden et al. (1998) also demonstrated that Grey-lag Geese moulting in the Netherlands could notmeet their daily energetic requirements duringmoult. In combination with use of field scores ofabdominal profiles to assess declines in fat stores(Owen 1981, Loonen et al. 1991), these authorsconcluded that geese relied upon fat deposits tomeet their energy requirements during moult.Analysis of stable isotope ratios in the new grownfeathers of the geese from Saltholm also suggeststrongly that some of the protein involved ingrowth of feather tissue must originate from bodystores accumulated prior to the moult period (un-published data). Greylag Geese moulting in Ice-land do not show significant changes in bodymass during moult (A. Sigfusson & C. Mitchellin litt.), hence, it seems that this species shows aflexible response to nutrient acquisition and wingmoult, depending on local conditions.

Is wing moult a period of energetic stress (sensuAnkney 1979) for the Greenland White-frontedGoose? What do the geese do during moult? Whathabitats are utilised? Are there any indicationsthat the nutrient requirements of the period andfinite habitat availability during this stage of theannual cycle could create density dependent limi-tations on the population in the future?

7.2 Moulting distribution and habitat

The non-breeding element of the GreenlandWhite-fronted Goose population moults in close

7 Moult of flight feathers

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proximity to the breeding birds. Since brood-rear-ing parents tend to be dominant over, and highlyaggressive towards, non-breeders, at a local scale,non-breeders are often displaced from the fa-voured brood-rearing habitats. Salomonsen (1950,1967) reported a northward moult migration ofnon-breeders, and there is no doubt that majornon-breeding moulting aggregations lie well tothe north of breeding areas where nesting densi-ties are highest. Greenland White-fronted Geesewere censused from the air in July 1992 and 1995between 67ºN and 72ºN (Glahder 1999). Thisstudy located important concentrations of moult-ers (figures in brackets indicate numbers of birdscounted from the air) on the Svartenhuk (72ºN,820-1,348) and Nuussuaq (70ºN, 634-1,003) penin-sulas, Disko Island (70ºN, 855-1,788), Naternaq(68ºN, 2,562-2,588), Eqalummiut Nunaat (67ºN,611-1,163) and Nasuttuup Nunaa (67ºN, 1,387).Mean flock sizes tended to be highest in the northof the range, which supports Salomonsen’s ideathat there was some moult migration northwards.However, overall densities were low (<1 goosekm-2) and varied considerably between areas andbetween years. In 1992, a cold spring and sum-mer, more geese appeared to summer in the cen-tral areas (66ºN-69ºN), but 1995 was warmer thannormal and geese were more numerous to thenorth and south (Glahder 1999).

Greenland White-fronted Geese characteristicallyuse lakes during the flightless moult period (whenthey forage on peripheral wetlands and take tothe safety of open water when threatened onland). The above-ground growth of the sedgeCarex rariflora becomes dominant in the diet dur-ing the flightless period (Madsen & Fox 1981).Carex rariflora is characteristic of sedge meadowsalong rivers, about the margins of lakes and inother open flat areas where water lies for longperiods during the melt. Such habitats were in-creasingly favoured by the geese and became thedominant habitat type during the early moultperiod (Madsen 1981, Madsen & Fox 1981, MS5).In Eqalummiut nunaat, during the latter part ofincubation, the large non-breeding element of thepopulation moved to high altitude to commencefeeding about the lake margins of the plateau(MS6). Here, they initially exploited those flat orsouth-facing areas first to thaw, finally movingto forage on the snow patch vegetation on north-facing slopes that were the very last areas to initi-ate young green plant growth in the landscape.Hence, even at this altitude, the geese were able

to follow the phenology of plant growth by lo-cally selecting between habitats.

Exploitation of such an altitudinal gradient is notpossible at several lowland sites exploited by thegeese in other parts of the range during the sum-mer. One such site is Naternaq (68ºN) where thegeese moult on lakes that contain abundant sus-pended glacial sediment and so support richemergent vegetation. Here the geese use emer-gent Equisetum, Carex and Eriophorum about theperiphery of the pools. This open expanse ofmarine sediments exposed by isostatic uplift sup-ports at least 2,600 breeding and moulting Green-land White-fronted Geese in a relatively smallarea. The geese exploit the numerous lakes andwetlands studded throughout a flat open plaincomposed of highly unstable fine glacial depos-its. Further north, there are important concentra-tions in the Sullorsuaq and Kuusuat areas onDisko Island, where the very high mountainousterrain restricts the geese to coastal areas, veg-etated outwash plains, vegetated valley bottomsand other lowland wetlands. The Disko Baycoastal strip northwards from Naternaq holdsmoulting birds at low densities, but high densi-ties occur only in small pockets further north-wards. The Nuussuaq peninsula is mostly highaltitude and unsuitable for geese, but the valleynorth of Sarqaq (Sarqaqdalen where Fencker(1950) made the first ever studies of breedingGreenland White-fronted Geese) holds highbreeding densities (Joensen & Preuss 1972). Thehigh central valleys of Nuussuaq (300 m abovesea level 70ºN) have supported up to 1000 non-breeding moulters (Glahder 1999). These areasprobably thaw too late to offer suitable habitatfor breeding birds, but the delayed thaw post-pones the early stages of plant production pro-viding suitable nitrogen rich food in the earlystages of growth during the moult. Further north,the terrain is very rugged and moulting geese areconfined to discrete coastal lowland areas withsuitable habitat, such as the extensive marshylowlands of the Svartenhuk peninsula.

7.3 Do Greenland White-fronted Geeseexperience nutrient stress duringmoult?

In terms of the Ankney (1979) definition of stress,Greenland White-fronted Geese do not appar-ently show outward signs of nutritional stressduring the moult period. Analysis of the body

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mass at different stages of regrowth of flight feath-ers shows no significant decline in the mass ofmales or females during the flightless period(MS17). Average body mass was approximately2.3 kg for females and 2.6 kg for males, close tothe minimum average for both sexes amongstcaptured birds in winter (see chapter 3). This sug-gests that most of the geese still retain modest fatdeposits throughout moult and are not approach-ing lean body mass at this time (i.e. that they re-tain some energetic reserve). The lack of any sig-nificant decline in body mass through the flight-less period also suggests that, amongst the caughtsample, there was no difficulty in obtaining nec-essary nutrients (particularly energy require-ments and specific protein/amino acids) at thesesites to sustain them through this period.

This pattern is similar to that found in other arc-tic nesting geese (e.g. Lesser Snow Geese andBrant, Ankney 1979, 1984, sympatric Greenlandmoulting Canada Geese MS17), in that geese re-tain little or no fat stores accumulated prior tomoult for use during the flightless period. How-ever, they show no decline in overall body masswhilst regrowing flight feathers. This is in con-trast to the trends described for Greylag Geeseon Saltholm and in the Netherlands (MS17, vanEerden et al. 1998), where 500-600 g of fat are ap-parently accumulated prior to this period. Whythe difference? One reason could be access to foodsupply. In arctic situations, growth in plants isdelayed relative to latitudes further south. Sincethe highest quality (particularly protein content)in above ground green parts of monocotyledo-nous plants is associated with the early stages ofgrowth, it may be that food is simply of betternutrient quality. However, geese in moult sitesabove the Arctic Circle can also forage through-out the 24 hour period, punctuated by shortpauses to rest, rather than showing a prolongedroosting period at 'night' (e.g. Barnacle and Pink-footed Geese, Madsen & Mortensen 1987, Green-land White-fronted Geese, Jarrett 1999). The in-terplay between nutrient absorption efficiencyand food retention time has been demonstratedfor geese (Prop & Vulink 1992). Hence, it wouldbe most efficient for a foraging goose to 'eat littleand often', filling the alimentary canal and rest-ing for short periods to extend the digestive pe-riod. The alternative would be to spend prolongedperiods with lower food retention times (i.e. withless efficient absorption of nutrients because of

high rates of throughput) and rest for a singleprolonged period at night. That Greenland White-fronted Geese change from an essentially diur-nal rhythm at other times during the summer (e.g.MS1, MS3, Madsen 1981, Stroud 1981b, 1982) tothe continuous feed/rest pattern typical of themoult supports this argument.

Based on the historical capture data (MS17), it istempting therefore to conclude that, given theability to feed throughout the 24 hours of day-light, Greenland White-fronted Geese may be ableto sustain their body weight without depletingreserves and complete moult without exploitingbody stores. At present, we have no means of as-sessing the carrying capacity of habitats used formoulting by the geese and hence no opportunityto assess whether the current population is ap-proaching the limit of moulting habitat availablein west Greenland at the present time. However,the availability and quality of food resources dur-ing moult is certain to be dependent upon pat-terns of thaw, and there is no doubt that the tim-ing of thaw varies considerably with season. In1999, when there was deep snow covering allhabitats down to sea level in early June north of69ºN, the extent of available moulting habitat waslikely to have been much more restricted than inmost years.

It is predicted that the climate in central westGreenland will become warmer in the very areaswhere the greatest densities of geese occur in sum-mer (Zöckler & Lysenko 2000, MS23). If thisproves to be the case, there may be a severe dis-ruption to the phenology of thaw, which currentlypermits geese to exploit the early growth stagesof different plant species following the sequenceof their release from snow patch areas as a conse-quence of aspect and local topography. Locally,elevated temperatures may enhance plant pro-duction. If climate change results in all habitatsin central west Greenland thawing earlier (espe-cially at high altitude) the flightless moultinggeese may 'miss' the best periods of above groundplant production if the geese are unable to modifytheir moult schedule. Conversely, the predictedcooling of summer temperatures in the north ofthe range could bring more summers with latesnow lie, decreasing the extent of available moulthabitat for birds using this region, and/or reduc-ing local quality and quantity of the food supply.

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7.4 Limits to suitable moulting habitatand potential inter-specificcompetition in the future

Since the mid-1980s, Greenland White-frontedGeese have faced a major change at their moult-ing sites. Canada Geese Branta canadensis interiorhave become established as a common breedingbird in areas of west Greenland previously onlyexploited by Greenland White-fronted Geese(MS13). Resightings and recoveries from ringedbirds have shown that these geese winter in theeastern United States, from Massachusetts andConnecticut south to Delaware and probablyoriginated from the Ungava Bay population ofCanada Geese that breed in northern Quebec(MS22). The Canada Geese arrive in late May andcommence nesting in habitats close to open wa-ter, so that there appears little competition in timeand space for breeding habitat between this spe-cies and the Whitefront. However, during themoult, White-fronted and Canada Geese use thesame habitats and areas to regrow flight feathers.At this time, both species are largely confined toareas within 50 m of open water. During thisphase in the life cycle, increased nutrient demandsand enhanced predation risk means there is anincreased potential for direct competitive effects.In sympatric situations, the diet of White-frontedGeese showed high niche overlap with the colo-nising species and included higher levels of poorquality bryophytes than at moult sites from whichCanadas were absent (Jarrett 1999, Kristiansen &Jarrett in Kristiansen 2001). Faecal analysis sug-gested that Canada Geese had a broad dietaryrange which changed little between sympatricand allopatric sites; in contrast, allopatricWhitefronts showed very narrow niche breadthscores based on faecal content, suggesting thisspecies is a specialist grazer (Kristiansen 1997,Jarrett 1999, Kristiansen & Jarrett in Kristiansen2001). It would therefore appear that Whitefrontscoexisting with Canadas switched to a more gen-eralised diet, perhaps in response to competitionfrom Canada Geese for favoured food items. Thetwo species appeared to segregate where theyoccurred together. In 45 agonistic interactionsbetween the species, Canada Geese won on everyoccasion, even when outnumbered. As a conse-quence, Whitefronts would stop feeding andadopt alert postures when Canada Geese ap-proached to within 3 metres (Jarrett 1999). In astudy area in Isunngua, numbers of both White-fronted and Canada Geese increased from 1988,but in the mid 1990s, Greenland Whitefronts be-

gan to decline, and have disappeared as moult-ing birds from many lakes favoured in this areawhere Canada now predominate. The resultsfrom extensive studies are about to be published(Kristiansen & Jarrett in Kristiansen 2001). How-ever, the implication from this study of a smallarea was that Whitefronts forced to moult withCanada Geese may be subject to exploitative com-petition as favoured plants are eaten out and in-terference competition when the dominant spe-cies physically prevent them from accessing po-tential feeding areas. Data from the 1999 aerialsurvey suggest that although both species showedhighest densities in the same Kangerlussuaq re-gion, at a local scale the two species were lesslikely to occur together than would be expectedby chance (MS23). Whether this is a consequenceof 'avoidance' competition or active exclusion re-mains conjecture.

7.5 Conclusions and discussion

The few studies of moulting Greenland White-fronted Geese suggest that these birds show noanticipatory accumulation of fat stores in prepa-ration for moult. Rather, they shed and regrowflight feathers at their lowest level of annual bodymass (equivalent to mid-winter minimum bodymass). Since most studied northern and arcticgeese show similar patterns, it is inferred thatGreenland Whitefronts can derive all the neces-sary energy and protein required to complete themoult from exogenous sources. This suggests thatunder studied circumstances, moult habitat wasnot then limiting.

On the other hand, the confinement of moultingbirds to the proximity of open water from whichthey can escape terrestrial predators inevitablyconstrains the amount of exploitable habitat avail-able to flightless geese. This has been found toequate to a potential feeding zone of at most 150m from water in other species (e.g. Madsen &Mortensen 1987, Kahlert et al. 1996) and possiblyless than 50 m in Greenland Whitefronts (Kristian-sen & Jarrett in Kristiansen 2001). This particularspatial limitation on foraging at this stage of theannual cycle suggests that this is a potential limi-tation on habitat availability on the summeringareas.

In July, the moulting geese are confined to partsof the landscape adjacent to water bodies to whichthey can escape to evade predators. The amount

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of available fresh green growth of graminoidplants with high protein at this time is limited inthe landscape as a whole and dependent uponpatterns of thaw. Global climate change couldpotentially interfere with the complex thaw gra-dients that ensure a sequence of protein rich foodis available. Increases in White-fronted andCanada Goose numbers could also reduce avail-able food resources to a level where nutrient avail-

ability could limit the numbers of moulting geeseable to replace flight feathers on individual sites.Studies of moult, it’s precise physiology, the in-terplay between diet and behaviour need to becarried out in different parts of the range if weare to determine whether these various factorsmay limit nutrient acquisition and affect the popu-lation in due course.

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8.1 Introduction

Almost all goose populations have increased inthe Western Palearctic in the last 45 years (Madsenet al. 1999). Since many of these are discrete andclosed populations, the increases cannot be ac-counted for by immigration of individuals fromelsewhere. These increases have not always beenbrought about by enhanced reproductive output,indeed for many populations, recruitment hasactually fallen with increasing abundance (e.g. theRussian-breeding Barnacle Goose populationEbbinge 1991, and see also chapter 6). Popula-tion modelling and simulation demonstrates thatas relatively long-lived birds, northern nestinggeese are sensitive to small changes in annualadult survival - very much larger changes in pro-ductivity rates are necessary to effect similarchanges in the rate of population change (e.g.Tombre et al. 1997, Pettifor et al. 1999). The sizeof a population is determined by the relative an-nual gain (birth rate and immigration) balancedagainst loss (death and emigration), hence it isnatural to accredit recent increases in abundanceto declining mortality rates. As a very high pro-portion of individually marked geese has beenrecovered as a result of hunting, it is assumed thathunting is responsible for a high proportion ofdeaths (e.g. Ebbinge 1991). Restrictions and com-plete banning of hunting on particular goose pop-ulations have resulted in immediate increases insome species including the Greenland White-fronted Goose (MS14). Others have shown lessimmediate responses after protective legislation(e.g. Russian Barnacle Geese Ebbinge 1991 andSvalbard Barnacle Geese Owen & Black 1999).Others still have shown long-term increases de-spite apparent increasing mortality (e.g. RussianWhite-fronted Geese Anser a. albifrons, Mooij etal. 1999) or sudden rapid increases not linked inany way to changes in hunting restriction (e.g.the Iceland/Greenland Pink-footed Goose, Mitch-ell et al. 1999). Hence, while it has been suggestedthat increases in numbers of some goose popula-tions are primarily due to the decreased mortal-ity rates resulting from reduction in shooting, thisis unlikely to be the sole factor influencingchanges in population size. However, there isevidence that adult annual survival rates havebeen greater under protection than in earlier pe-

riods when the geese were subject to hunting ex-ploitation (Ebbinge 1991, MS14).

This relationship is important in order to under-stand the nature of hunting mortality if restric-tion on shooting kill is to be used justifiably as amanagement tool to achieve nature conservationmanagement goals. It is necessary to understandthe extent to which the number of deaths causeddirectly through hunting add to natural mortal-ity (additive mortality), rather than being com-pensated for through a consequent reduction innatural loss through some density-dependentfunction (compensatory mortality, see discussionin Anderson & Burnham 1976, Nichols et al. 1984,Newton 1998). In order that hunting loss is di-rectly compensated for by reductions in naturalmortality, natural loss must already be densitydependent and the kill cannot take place after themain period of natural loss. Hence the impact ofthe hunting bag in terms of the mortality in addi-tion to natural loss depends on both the numberskilled in the hunt, the seasonal timing of bothlosses and the degree of density dependence in-volved in natural mortality. However, to demon-strate such a mechanism is important – if hunt-ing mortality were completely compensatory,protection of a hunted population would not re-sult in an increase of numbers. Conversely, dem-onstrating that mortality is completely additiveenables restriction of hunting kill to be used as atool to directly influence population size, control-ling for reproduction rates. Hunting mortalitymay ultimately become partially additive to natu-ral losses, i.e. at low levels, this would have noeffect on the total annual death loss but above acertain density threshold, extra hunting mortal-ity does contribute to a reduction in survival.

Serious declines in the numbers and range of theGreenland White-fronted Goose were attributedto habitat loss and the effects of hunting in the1980s (Ruttledge & Ogilvie 1979). This led to theprotection of the population at most haunts onthe wintering grounds and ultimately to the draft-ing of a management plan for the population(Stroud 1992). The geese had been legal quarrythroughout its range (West Greenland breedinggrounds, Iceland staging areas and winteringquarters in Britain and Ireland) until the early

8 Survival

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1980s. They are now protected from hunting inBritain and Ireland (since 1982) and the seasonhas been shortened to 16 August-30 April inGreenland (from 1985). Immediately followingthe implementation of protective legislation,numbers at the two most important winteringsites (Islay in the Inner Hebrides, SW Scotlandand Wexford Slobs, SE Ireland) increased, sug-gesting that hunting was at least partially addi-tive to overall natural losses. Observations of in-dividually marked birds have shown that thepopulation tends to be site loyal: only 14% of birdsseen in consecutive winters changed site and 7%per annum showed permanent emigration (MS7,MS9, M. Frederickson unpublished data). Sincehunting took place at both sites up to the time ofprotection, these cases offer an opportunity toexplore the effects of changes in hunting legisla-tion on the numbers using these sites. At Wex-ford, hunting was permitted again in the wintersof 1985/86 and 1989/90. In this chapter, an at-tempt is made to determine the role huntingplayed in limiting numbers of Greenland White-fronted Geese at Wexford, using census data andreviewing various different approaches to theestimation of annual survival in this population.

8.2 Were annual adult rates of return toWexford related to the size of theannual kill?

Counts of Greenland White-fronted Geese havebeen carried out at Islay and Wexford since at leastthe winter of 1967/68. Since 1982, carefully co-ordinated monthly counts have been carried outfollowing a standard procedure at both sites (seeEasterbee et al. 1990, Fox et al. 1994, MS14 fordetails). In years prior to this, up to 40 counts werecarried out on Wexford Slobs in each winter, andat least two complete counts of Islay were under-taken annually. Large samples of birds have beenaged in each autumn since 1968/69 to determinethe proportions of first-winter birds present dur-ing early autumn or winter. It is important tounderstand whether the magnitude of the annualhunting kill was responsible for changes in theprobability that a bird would return to either sitein the following year.

Based on the annual maximum count from eachwinter (N) and proportion of juveniles in thepopulation J for each winter t, an assessment ofapparent annual adult return rate Rt for Wexfordand Islay was determined as follows:

Rt = (Nt – JtNt)/Nt-1 (1)

This measure includes the net balance of immi-gration/emigration of individuals to each site aswell as true survival between years. Furthermore,the measure suffers from sequential bias, in thatan overestimation of apparent survival in year tis compensated for by an underestimation in yeart+1. However, as far as the numbers of geese re-turning to the site is concerned, this measure hassome utility in determining the way in which lo-cal abundance at a site varies over time. It seemslikely that changes in annual immigration/emi-gration rates are relatively small, and probablyrelatively constant, so that annual adult rate ofreturn to a wintering resort represents a proxymeasure of annual adult survival. Is it possible todetect a change in annual adult return rate thatcan be related to the number of birds killed inany one year? Although not evidence of directlyadditive mortality, such change would supportthe argument that hunting at a known level hasan impact upon the probability of a bird return-ing to a wintering site in a subsequent year.

At Wexford Slobs, the hunt was always limitedin time and space, and the size of the bag deter-mined for each year. Estimates of the numbersshot in Wexford Harbour were less precise, soannual totals killed there were estimated basedon observations and discussions with wildfowlersin each season and these totals added to thosekilled at the Slobs. When the moratorium onshooting was lifted in 1985 and 1989, the bag wasstrictly limited and the numbers shot were re-corded. In 1981/82-1983/84, a detailed study wasundertaken to assess the level of mortality on theWexford Slobs. Systematic (but not comprehen-sive) searches were carried out using a trainedretriever dog on the Slobs and along the shoresof Wexford harbour to find the bodies of unre-trieved dead and dying geese. In 1981/82, whenhunting took place, 28 geese were found in thisway (in addition to the 142 reported shot), com-pared to none in following years with protectionfrom shooting (D.W. Norriss in litt.). For this rea-son, in all years when hunting occurred, an addi-tional 20% was added to the known bag to allowfor geese mortally wounded or not retrieved(based on general experience from many yearsand specific investigations during 1981/82). Inthis way, an annual kill was defined (Kt) for eachyear with hunting at Wexford. The number ofbirds killed Kt was then expressed as a propor-tion of the maximum numbers recorded Nt to give

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the hunting mortality rate Kt for year t and plot-ted against adult annual return rate Rt for thatseason. Under the additive mortality hypothesis,it would be predicted that annual survival rate(and hence adult return rate) decreases with in-creasing kill rate in a linear fashion (away from K= 1 where the linear relation is a poor approxi-mation, see Anderson & Burnham 1976). Underthe hypothesis of completely compensatory mor-tality, annual return rate would be independentof variation in kill rate up to a threshold pointwhere further increases in kill rate must result inreduced annual survival (Anderson & Burnham1976). These two states represent extremes, withthe slope b in the equation:

R = R0 (1-bK) (2)

In this case R represents annual adult return rateand R0 represents this measure when no huntingoccurs. The slope b would be equal to unity incomplete additive hunting mortality and zeroover the range of realistic hunting kill rates incomplete compensatory hunting mortality. Notethat this analysis only considers compensatorymortality as this relates to winter hunting killsince, by definition, the term R0 includes the hunt-ing kill, which occurs in Iceland and Greenland,as well as 'natural' mortality. In this analysis, R isplotted directly against K and a regression modelapplied of the form:

R = R0 -BK (3)

The slope B was tested for significant differencesfrom the predicted b values of 0 (perfect compen-sation) and 1/R0 (completely additive huntingmortality) using t tests.

The annual adult survival rate of GreenlandWhite-fronted Geese wintering at Wexford wassignificantly negatively correlated with kill rateduring the years 1970-1999 (Figure 8.1). This re-gression model explained more variance than thebest quadratic fit. A quadratic fit would implyinitial (i.e. partial) compensation to a thresholdabove which hunting mortality is totally additive.The slope did not differ significantly from theexpected value of 1.129 (i.e. 1/R0, t26 = 0.276 P >0.05), but was significantly different from zero (t26= 2.94, P < 0.01). Mean apparent survival duringthe years with hunting (0.817 ± 0.021 SE) was sig-nificantly lower than in years without (0.884 ±0.016 SE, t26 = 2.48, P < 0.01).

It is clear that the annual adult return rate is not agood measure of survival rate, including as itdoes, the balance between immigration and emi-gration in the Wexford wintering populationwhich is not a 'closed' one. However, these datado strongly suggest that the return rate was di-rectly related to the size of the kill over the pe-riod that data are available, in a way that closelyresembles additive mortality.

8.3 Modelling long term changes inannual adult return rates to Wexfordassuming additive mortality

Given the low variation in the annual probabilitythat a bird returns to winter at Wexford and therelationship between this property and annualhunting kill, it seems sensible to construct a verysimple population model assuming constant an-nual adult return rate. In this way, given the ob-served numbers of young in each winter, it ispossible to generate the expected numbers ofadults in year t+1 based on total numbers in yeart. The assumption is made that, for the Wexfordwintering group of Greenland White-frontedGeese, (i) natural survival and (ii) the balance ofbetween-year immigration and emigration are notyear specific (i.e. in the absence of hunting, an-nual adult return rate is constant). In generatingdata for those years with hunting, it is furtherassumed that hunting mortality is completelyadditive, so that, in the years with hunting, an-nual adult return rate is the expected returning

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Hunting mortality (%)

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de a

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pre 1982 hunting

regression

post-1982 hunting

protected in winter

Figure 8.1. Plot of crude annual survival rate (basedon adult return rates from annual census data – seetext for full details) against hunting mortality rate(known bag plus 20% unretrieved losses expressed asa percentage of the peak winter count for each year).There was a statistically significant inverse correlationbetween these two measures11.

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number of birds less the hunting kill. Using onlythe initial maximum population count for the year1967/68, and the mean apparent annual adultsurvival rate R0 (derived from equation 3 above),the population size for each successive year t+1was calculated as follows:

Nt+1 = (R0Nt (1+Jt+1)) – Kt+1 (4)

where Kt+1 represents the hunting kill in year t+1,since maximum numbers usually occur at Wex-ford in mid winter after the finish of the hunt(MS9). We defined Kt+1 as the number of geeserecorded shot at Wexford Slobs and Harbour eachwinter plus 20% (see above). The model was thenused to generate changes in population size givenobserved values for Jt+1 up to 1999.

Substituting a constant annual apparent adultsurvival rate of 0.884 throughout in the simpledeterministic model produced a remarkably goodfit to the data until 1990 (Figure 8.2). Althoughapparently overestimating population size slight-ly in the early 1970s, the model shows good corre-spondence to the observed values during the pe-riod before and after hunting was banned at Wex-ford. After 1990, the model no longer describesthe population development. As there has beenno resumption of hunting in Ireland, this is notlinked to shooting mortality on the winteringgrounds. Rather, it is known from individualmarking that 75% of the 1989 cohort of markedjuveniles failed to return to the wintering groundsthe following season, and adult mortality was also

10% higher that year (see next section). If the col-lared birds were representative of the winteringnumbers at Wexford as a whole, this would haveresulted in some 1900 fewer birds returning inwinter 1990/91. If this exceptional loss is addedin to the model, the fit is greatly improved (seeFigure 8.2).

This approach is extremely simplistic and no at-tempt has been made to test goodness of fit ofthis model against alternative models. Neverthe-less, the results underline the sensitivity of suchlong lived birds to small changes in annual sur-vival/return rates. The simple model using a con-stant annual adult return rate (88.4% percent perannum) and the assumption of completely addi-tive hunting mortality to the Wexford winteringsite described the population changes extremelywell in the period prior to and immediately fol-lowing the cessation of hunting at this site. Theanomalous deviation in very recent years appearsto be at least partly explained by a year of verylow survival, especially amongst juveniles, fol-lowing the summer of 1990, known from popu-lation trends elsewhere and from lowered sur-vival rates of neck-collared birds. There is thusreasonable evidence to suggest that hunting atWexford may have been additive for the years1970 to protection on the wintering grounds in1982, and that the levels of kill experienced in thatperiod resulted in no clear trend in numbers(MS14). However, with the cessation of hunting,Wexford numbers immediately increased, consist-ent with expectations if hunting mortality wasadditive at this site. Very recent stabilisation andslight declines in the numbers of geese winteringat Wexford are consistent with a high mortalityevent after winter 1989/90 and with observeddeclines in fecundity there (see chapter 6).

8.4 Current measures of annual survivalrates based on individual histories

The first attempt to measure adult annual sur-vival rates in Greenland White-fronted Geese wasby Boyd (1958), using the Haldane (1955) method(as the numbers of geese ringed were not known).He estimated annual adult survival to be 66.1%(± 3.6 SE) based upon ringing recoveries of birdsringed and recovered (based largely on huntingreturns) during 1946-1950. Subsequent analysisusing similar methods for all recoveries from1946-1974 found survival rates of 76.7% (± 3.4 SE,MS6). Both of these estimates were generated

Figure 8.2. Model of changes in abundance of Green-land White-fronted Geese wintering at Wexford Slobs,based on constant annual adult rate of 0.884 ( ), com-pared with the actual annual census counts for theyears 1967/68-1998/99 ( ). The outputs from themodel incorporating the low survival of birds knownfrom losses of collared individuals following the win-ter of 1988/89 are shown as . See text for full details.

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1965 1970 1975 1980 1985 1990 1995 2000

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during the period when the population was le-gal quarry in Greenland, Iceland, Ireland and Brit-ain, although we have little idea of the precisesize and distribution of the harvest at that time.By way of comparison, the survival rate for theperiod 1990-1997 (using only the recovery datagenerated from the collar-marking scheme) wasanalysed using the Haldane methods and gavean annual survival rate for the period of 81.7% (±0.8 SE, H. Boyd, in litt.). The 5% difference in sur-vival rate is very similar to the mean huntingmortality rate prior to protection (see Figure 8.1).

It was considered that the survival rate of Green-land White-fronted Geese prior to protection wastoo low to sustain the then level of hunting kill(e.g. Owen 1978). For that reason much bureau-cratic and political effort was put into removingthe subspecies from the quarry list, especially onthe wintering grounds. As described earlier, thisled to the effective protection of the populationfrom hunting on the wintering areas from 1982onwards (see MS14, Stroud 1992 and Fox et al.1999 for full details). Evidence from counts ofbirds at a number of wintering sites strongly sug-gested that the increase in numbers that followedthe cessation of winter hunting was due to theincrease in return rate of birds, not to changes inreproductive success (MS14). Indeed, we are nowaware that since protection, breeding success hasactually decreased amongst the Wexford and Is-lay wintering elements of the population, whichprovides more evidence that restriction on hunt-ing has increased annual survival.

There was no extensive visible marking pro-gramme in effect before and after the implemen-tation of protection in winter. This would haveallowed a more sensitive monitoring of changesin survival based on individual bird histories andthus enable the interpretation of subsequentchanges in overall population size. The capture-mark-recapture study using neck-collared birdsinitiated in Ireland only commenced after protec-tion had been implemented. Using the resightingsof neck-collared birds marked at Wexford during1984-1989, Bell et al. (MS10) calculated annualadult survival using SURGE4 models (Clobert etal. 1987, Pradel et al. 1990) to generate maximumlikelihood estimates of 78.5% (± 1.4 SE). This com-pares with 72.4% (± 7.3 SE) based on ringing re-coveries from the same ringing programme us-ing BROWNIE (Brownie et al. 1985). Using theHaldane method on birds marked in the winterperiod gives a survival estimate of 72.1% (± 1.1

SE) for the period 1984-1989 (H. Boyd in litt.) TheSURGE models use much more fine-grained in-formation and provide year- and age-specificmaximum likelihood estimates, based on data-rich repeated resighting histories of individualbirds. The Brownie techniques utilise the geesecaught, ringed and never retrieved again to esti-mate reporting and recovery rates in a more so-phisticated survival estimation than the Haldanemethod. It is not possible to use the Brownie etal. methods on the 1940s data, because some ofthe original capture and ringing data do not ex-ist.

More recent analysis has been carried out using acombination of recoveries and resightings of col-lared birds at Wexford using MARK (White &Burnham 1999, based on the recovery-recapturemodels of Burnham 1993 and multi-stage mod-els of Hestbeck et al. 1991). The selected modelwas one of survival, which varied with year in-dependently for adults (weighted mean 78.5%,see Figure 8.3) and juveniles (67.8%, but whichshowed greater variability, Figure 8.4), with amean of 7% permanent emigration per year (M.Fredriksen & A.D. Fox unpublished). There wasno effect of hunting on annual adult or juvenilesurvival estimates in the two winters (1985/86and 1989/90) when the moratorium was lifted atWexford, although the survival rates in the yearfollowing 1989/90 were the lowest for adults andjuveniles (Figures 8.3 and 8.4). In 1990/91, only 7out of a marked cohort of 33 first winter juve-

Figure 8.3. Annual adult survival rate (+ 95% CL) forGreenland White-fronted Geese caught at Wexford,1983/84-1997/98 based on observations and recover-ies of neck-collared individuals using the MARK suiteof programs (see text and Appendix 1 for details)12.Open symbols indicate those seasons when the hunt-ing season was opened at Wexford for a limited shoot.The unusually low survival estimate and large confi-dence intervals for 1983 probably reflect small samplesizes in that year.

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al r

ate

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70

niles marked in the previous winter were everreported again, a remarkably low annual returnrate (21%). One of them was reported from Penn-sylvania, in the eastern United States in Decem-ber 1990. It may be that the low survival rate thatseason was due to geese encountering severeweather (for example a storm in autumn 1990 thatblew them westwards off track). The Lamb dailyclassification of weather systems over the BritishIsles for that period shows no obvious anomaliesthat could account for this extraordinary loss (H.Boyd. in litt.)

Based on these two years, there is no evidencefrom the probability of birds shifting from Wex-

ford to Islay (e.g. Figure 8.5) or elsewhere, thatGreenland White-fronted Geese were more likelyto emigrate from Wexford in winters followingthose with an open shooting season. Hence, thereis no evidence to suggest that the opening of theseason in very recent years has had a demonstra-ble additive effect on annual adult survival rateor has enhanced emigration rate.

8.5 Conclusions and discussion

Ruttledge & Ogilvie (1979) suggested that the lossof peatland habitat might have concentratedGreenland White-fronted Geese into areas wherethey were easier to shoot. Not only would thishave had an adverse effect on survival rates, butit would also have made them more sensitive tohunting disturbance. Human disturbance in gen-eral has since been shown to have a major influ-ence on the size and trends in numbers of severalflocks (Norriss & Wilson 1988, 1993, MS14). Informer times, the bogs and moorlands they ex-ploited would have provided food, daytime rest-ing areas and nighttime roosts all with very littledisturbance. It would therefore seem likely thatthe extensive historical loss of such feeding sitesfor wintering flocks and increasing levels of dis-turbance, reduced their ability to acquire neces-sary stores to survive and reproduce at that time.It does seem likely that habitat loss in such a site-faithful population made it more vulnerable tohunting and disturbance. Since hunting does ap-pear to have a direct depressing effect on overallsurvival rate, it seems more likely that increasedsusceptibility to hunting (prior to the 1980s)caused the declines and extinctions that occurredthen. Nevertheless, reduction in breeding outputthrough failure to accumulate sufficient bodystores could also have resulted from the increaseddisturbance experienced at unfamiliar winteringsites. However, we shall never know preciselyhow changes in habitat availability affected thedemography of the population and caused thechanges in local wintering numbers at specificsites.

There is no doubt, however, that despite contin-ued loss of traditional peatland feeding areasduring the latter part of the 20th Century, theGreenland White-fronted Goose proved itself asable as other grey geese to exploit new and novelagricultural habitats. Flocks initially moved torough pastures and flooded grassland, but latterlyhave also exploited intensively managed grass-

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1982 1984 1986 1988 1990 1992 1994 1996 1998

Est

imat

ed a

nnua

l juv

enile

sur

viva

l rat

e

Figure 8.4. Annual juvenile survival rate (± 95% CL)for Greenland White-fronted Geese caught at Wexford,1983/84-1997/98 based on observations and recover-ies of neck-collared individuals using the MARK suiteof programs (see text and Appendix 1 for details)12.Open symbols indicate those seasons when the hunt-ing season was opened at Wexford for a limited shoot.Note the unusually low survival rate of geese markedas goslings in 1988/89 that was not linked to huntingkill in that season.

0

0.1

0.2

0.3

0.4

0.5

1980 1985 1990 1995 2000

Pro

babi

lity

of m

ovin

g be

twee

n si

tes

Wexford to Islay

Islay to Wexford

Figure 8.5. Transition probabilities for GreenlandWhite-fronted Geese moving between Wexford andIslay and vice versa for each year from 1983/84-1997/98. There are no significant trends in the movement ofindividually marked birds over the period based onobservations of neck-collared birds12.

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71

lands. This process was certainly underway whenthe geese began to exploit the newly createdSloblands in Wexford Harbour (probably at oraround 1910, Ruttledge & Ogilvie 1979), despitethe complete absence of boglands in the vicinity.

Despite their traditional habitat and high wintersite fidelity, these geese have shown an ability toexploit new habitat opportunities. That said, onlyone flock of White-fronted Geese is known to havecolonised and established an entirely new win-tering site since 1982. The process of exploitinggrassland habitats, either those that are semi-natural or of low intensity agriculture, has con-tinued to the present day. Although many flocksstill resort to peatland habitats to feed and sleepat night, there are few flocks remaining that ex-ploit bogs by day (MS14, MS24). Norriss & Wilson(1993) argued that this transition to more agri-cultural grassland was not forced upon the geeseby habitat loss in very recent times, but that thegeese responded to the creation of more profit-able feeding habitats without loss of traditionalones. This change has been occurring graduallysince the 1950s, and therefore does not coincidewith the dramatic increase in numbers that hasoccurred since protection from hunting. Hence,while it is possible to argue that increases in totalnumbers since the 1970s have been associatedwith increasing use made by the population ofmore intensively managed farmland, this cannotbe anything more than a contributory factor ena-bling contemporary increase, rather than the spe-cific cause. This is further supported by the factthat the population range has effectively re-mained the same in the last 20 years, althoughseveral winter flocks have disappeared.

This ability to adapt to the exploitation of newhabitats may be linked to the availability of suchhabitats in the neighbourhood of traditional flockranges. In areas of Scotland where extensive ar-eas of intensively managed grassland are avail-able (e.g. Islay, Kintyre, Stranraer), GreenlandWhite-fronted Geese have switched to thesewhilst retaining traditional roosts. This processhas presumably run in parallel with improvinggrassland management practices since the early1960s. In areas with little intensive grasslandmanagement and no tillage (e.g. many of theHebridean islands such as Jura, Mull, Skye andLewis) flocks remain small (see land use classifi-cation maps in Mackey et al. 1998). Equally, inareas with suitable extensive arable and managedgrassland but no traditionally used roosts, the

species is totally absent (e.g. in Ayrshire and largeareas of Dumfries). However, flocks with winter-ing areas with the greatest area of improved grass-land within traditionally used areas have tendedto show increases in their number. This is in con-trast to those flocks where land use has changedlittle, or agricultural land has been abandoned.In this way, there appears some fitness conse-quences to the availability of managed grasslandwhich affects the rate of change in local winter-ing numbers, although it is far from clear if theserelate to annual adult survival, reproduction orrates of immigration/emigration. Investigationsof these parameters in relation to habitat and in-dividual quality remain a priority for future re-search.

In contrast, it would appear from the evidencepresented here and in MS14 that, prior to protec-tion, the numbers of birds wintering at Wexfordand Islay were limited prior to protection by thenumbers shot. These two sites have held some60% of the population since protection, hence thislimitation was a significant one. There are no ac-curate collated hunting statistics for Islay. Sinceprotection on the wintering grounds in 1982, thereturn rate of birds to Wexford and Islay has beenmore or less constant. At Wexford, incorporatingthe numbers killed into a simple model suggeststhat the return rate has not changed since the late1960s. Hence the product of annual survival andemigration/immigration balance has remainedconstant at around 88.4% over 3 decades of large-scale land-use change. The relative stable num-bers during 1968-1982 seem to have been due tothe balance between hunting off-take and changesin annual breeding success. Immediately afterprotection, numbers increased consistent with thesame probability of annual return rate. In the ab-sence of the hunt, this resulted in the increasednumbers. The increase has continued at ratesregulated by the potential of reproduction to re-place lost individuals.

Since the start of the 1990s, the numbers winter-ing at Wexford have shown signs of decline dueto falling fecundity (chapter 6) and to catastrophiclosses of young and their parents in 1990, hencedeclines in reproduction appear now to be limit-ing the numbers at Wexford. Since the reductionin fecundity is mirrored amongst the winteringnumbers on Islay and perhaps other winteringareas as well, this seems to be a general phenom-enon in the population as whole in recent years.On Islay, the reduction in reproduction rate has

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72

not yet been sufficient to halt the linear annualincrease in numbers since protection.

The Greenland White-fronted Goose was a popu-lation that was declining due to habitat loss andhunting, but where protection from hunting hasincreased survival in proportion to the former sizeof the hunting bag, enabling the population toenter a phase of increase. Apparently confined to

traditional areas by behavioural site loyaltythroughout its range, the population has shownsigns of slowing its expansion in numbers in veryrecent years due to declining reproductive success.

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9.1 Anticipatory acquisition of nutrients,density dependence and constraintsupon fitness

In spring, every female Greenland White-frontedGoose of breeding age must clear three nutritionalhurdles in order to breed successfully. The annualcycle involves completion of two spring migra-tion episodes. Both require the bird to make thenecessary physiological and anatomical modifi-cations and lay down fuel reserves to sustain twoflights of 1,500 km, one over the sea to Iceland,and the second crossing the sea and the Green-land Ice Cap. The ease with which an individualcan clear these hurdles has various fitness conse-quences. Failure to construct large enough flightmuscles or energy stores to sustain the flight willresult in death en route – this much natural selec-tion will ensure. However, the ability to accumu-late the necessary resources to only just completethe two flights leaves no stores for investment inreproduction. Slow accumulation of adequatestores will delay departure from staging areas and

time of arrival to the nesting grounds, so condi-tion mediated timing of breeding may also affectreproductive output in this way. To complete thejourney to the breeding grounds early enoughwith some extra stores remaining is likely to con-tribute to the investment in reproduction, andthis, together with efficiency in finding food dur-ing the pre-nesting period, is likely to determine,to a major extent, the reproductive success of thatindividual.

On the other hand, there must be some upperlimit on the amount of energy or other nutrientstores, set by the cost of carrying such excess bodymass (e.g. predation risk and enhanced energyuse induced by heavier flying weight, see reviewin Witter & Cuthill 1993). Nevertheless, the abil-ity to acquire specific nutrients to store for use atkey points in the winter and spring has conse-quences for the ability of a bird to reproduce, or,in the extreme, to survive each migration. Theefficiency (and therefore the rate) of accumula-tion of such 'capital' through a series of acquisi-

9 Synthesis

Lipid costs of egg laying and incubation

Costs � bodymass (kg)

BMR(kJ)

Lipid equivalentof 1xBMR

(g/day)

DEE(xBMR)

Laying/incubation

period(days)

Lipid used inlaying/

incubationperiod

(g)

Lipidused inclutch

(g)

Totalminimum

andminimum

lipidinvestment

(g)

Laying 2.78 690 18.2 1.7 4-8 123.5-247.1 49-98 172.5-345.1

Incubation 2.78 690 18.2 1.1 26 519.6 519,6

Protein costs of egg-laying and incubation

Costs � bodymass (kg)

Maintenanceprotein(g/day)

Laying/incubation period

(days)

Protein used inlaying/incubation

period (g)

Protein used inclutch

(g)

Totalminimum

andminimum

proteininvestment

(g)

Laying 2.78 5.7 4-8 23.1-46.2 56-112 79.1-158.2

Incubation 2.78 5.7 26 165.0 165.0

Table 9.1. Protein and lipid energy requirements for a laying Greenland White-fronted Goose, her clutch of3 or 6 eggs and subsequent incubation. Analysis follows methods of Meijer & Drent (1999), using BasalMetabolic Rate estimated from the relationships for non-passerines derived by Aschoff & Pohl (1970), i.e.BMR = 330.W0.722 (where W = body weight in kg.) and based on the assumption that daily energy expendi-ture (DEE) during laying is equivalent to 1.7 x BMR. Protein costs were calculated using the modifiedformula of Robbins (1981) related to body weight according to the formula 2.68.W0.75 g protein day-1 (seeMeijer & Drent 1999 for full explanation).

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tion and depletion events has therefore the po-tential to influence the fitness of individuals.

Let us assume that we can use body mass as cur-rency to reflect the 'adequacy' of stores accumu-lated by an individual to complete migration toIceland and onwards to Greenland. In this way,we can diagrammatically represent the mass tra-jectories of individuals which exhibit differentrates of accumulation of such stores under thesame environmental conditions (Figure 9.1). Bodymass may in reality represent a proxy measure ofenergy stores in the form of fat deposition, orperhaps storage of a scarce resource, such as theprotein required to develop the musculature re-quired for flight. If such a representation reflectsreality, small differences in the rate of accumula-tion of such stores can potentially have a cumu-lative effect on individuals throughout the courseof the spring, with knock-on effects from each ofthe resource 'hurdles' encountered.

The accumulation of stored mass is relatively slowin winter, but failure to reach high enough thresh-olds by departure from wintering areas leavesinsufficient opportunity to recoup stores in Ice-land. Hence, differences in individual quality (interms of ability to acquire such reserves at criti-cal periods) can affect the amount of mass accu-mulated and the amount available for investmentin migration and ultimately reproduction.

This model is useful when compared with actualdata compiled in the previous chapters. If the costof egg production in Greenland White-frontedGeese is calculated using the methods of Meijer& Drent (1999), it is possible to estimate the massrequired to produce a clutch of 3 or 6 eggs andthen to incubate these (Table 9.1). Using the fieldestimates of abdominal profiles as a crude indexof body mass throughout the period, it is possi-ble to construct a graph of changes in mass ofadult male and female geese up to the point oflaying. The investment by the female in clutchproduction and incubation can then be assessedrelative to the body mass available at the point offirst egg production (Figure 9.2). From this, it canbe see that the costs of laying a clutch of 6 eggstakes the 'median' level of female body mass wellbelow the lowest weights recorded throughoutthe annual cycle. This level is presumably wellbelow lean body mass and hence represents star-vation levels, even before the costs of incubationare considered. Although costs of self-mainte-nance during incubation are offset by feeding

Figure 9.1. Patterns of theoretical accumulation of storesby adult female Greenland White-fronted Geese dur-ing the first 5 months of the year. Trajectories repre-sent 4 different individuals that differ in their rate ofaccumulation of stores (because of feeding efficiency,behavioural dominance, parasite load, etc.). If birds failto accumulate sufficient reserves to reach a particularthreshold at winter departure, they may fail to reachIceland (individual 'd'), or do so with insufficient storesand too little time to accumulate stores to complete thejourney to the west coast of Greenland (individual 'c').Even if accumulated stores are sufficient to support theflight successfully to the breeding areas, the individual'b' still cannot accumulate stores rapidly enough post-arrival to the level required to initiate a clutch (shownby 'A' above), hence she incurs a fitness cost in termsof failed breeding. There will be a range of breedingoptions available to the female dependent upon thelevel of energetic reserves at the commencement ofbreeding. Hence, within the band “A” the timing andextent of nutrient acquisition will affect reproductiveinvestment through factors such as manipulation offirst egg date or clutch size. It is also possible that birdsarriving in Greenland and acquiring sufficient nutri-ents on the pre-nesting areas to invest in a clutch maypotentially affect the relative quality of her investment.This has consequences for her reproductive output (interms of her egg size, clutch size, incubation constancy,etc.). Seen in this way, small differences in feeding effi-ciency, and hence accumulation of stores, can be seento have a cumulative effect during the five or so monthsbefore first egg date. This is why the sward type a birdfeeds upon, or the feeding efficiency of an individual,or the level occupied by the individual in a dominancehierarchy may have such consequences in terms of fit-ness measures. Note also that the critical periods ofstore acquisition are those in Iceland and Greenland,where rates of accumulation are most rapid and there-fore where small perturbations are likely to have mosteffect. Note also however, that even during the slowaccumulation of stores on the wintering grounds, fail-ure to accumulate stores bears a future cost, insofar asthe short episodes of rapid store accumulation in Ice-land and Greenland do not permit individuals to 'catch-up lost ground' at these later stages in the spring pe-riod.

LEV

EL

OF

NU

TR

IEN

T S

TO

RE

S

Staging inIceland

Pre-nestingfeedingGreenland

Mortality

Aa

b

c

d

Winter accumulation of stores

JAN FEB MAR APR MAY

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during recesses from the nest by the female, thesebouts are rare and of short duration (see chapter6). It would therefore seem that, based on obser-vations of the 'median' female and the calcula-tions presented here, meeting the energetic andnutritional costs of laying a clutch and complet-ing successful incubation is not possible. On thisbasis, most females in any given year are unlikelyto attain nutrient and energy thresholds neces-sary to reproduce. That said, observations fromseveral years indicate considerable individualvariation in abdominal profiles between individu-als. Indeed, some birds show considerably fasterrates of accumulation of body mass than do oth-ers. It seems likely, therefore, that only those rela-tively few individuals able to accumulate storesat rates well above the mean throughout the prel-ude to breeding will therefore have the potentialto attempt to breed. On this basis, it would ap-pear that a large proportion of geese could po-tentially arrive in west Greenland having failedto reach threshold condition for successful repro-duction.

The crucial questions, therefore, concern themechanisms that are likely to affect the ability ofthe individual to acquire the necessary nutrients

for survival and reproduction at each criticalstage. Assuming that the environment is not un-limited in its ability to supply nutrients, a criticalfactor is likely to be the local density of geese.This factor affects the ability of an individual toachieve threshold nutrient requirements. Whatfactors enable some individuals to survive andbreed whilst others cannot? There is abundantevidence that amongst relatively long lived avianspecies such as geese, breeding performance in-creases with age (e.g. Owen 1984, Forslund &Larsson 1992, Cooke et al. 1995). More older birdsattempt to breed than among young age classesand a greater proportion of older birds breed moresuccessfully. For example, Raveling (1981) foundalthough geese 4+ years of age comprised 26% ofthe potential breeding population, they producedmore than 50% of young in Giant Canada GeeseBranta canadensis maxima. Specifically, older birdslay earlier, larger and heavier clutches than youngbirds, which ultimately result in more offspringfledged.

However, reproductive performance in geese gen-erally increases only for the first 5-6 years of life(Rockwell et al. 1983, 1993, Forslund & Larsson1992). This is not consistent with the hypothesisof reproductive restraint in younger years (Curio1983), which would predict increasing reproduc-tive effort throughout life. It would therefore ap-pear that in many goose populations, young in-dividuals are constrained from performing well,perhaps through the lack of social status that per-mits access to best feeding opportunities.

Dominance hierarchies have long been recognisedin goose flocks (Boyd 1953, Hanson 1953, Raveling1970) and rank has been shown to increase withage (Lamprecht 1986, Black & Owen 1995). How-ever, amongst birds of the same age class, domi-nance explained much of the variation in repro-ductive performance, suggesting this was theoverriding factor (Lamprecht 1986, Warren 1994).Most evidently, dominance determines individualfeeding opportunity through securing and de-fence of best feeding opportunities (e.g. Teunissenet al. 1985, Prop & Loonen 1988, Prop & Deeren-berg 1991, Black et al. 1992). This in turn has con-sequences for food intake rates, since peck ratesand feeding rates have been found to correlatepositively with dominance (e.g. Warren 1994).Social status also affects whether a goose pair isable to obtain and hold a nesting territory. In situ-ations where predation limits output, hatchingsuccess and fledging rate were also correlated

1200

1600

2000

2400

2800

3200

3600

early

Jan

late

Jan

early

Feb

late

Feb

early

Mar

late

Mar

early

Apr

late

Apr

early

May

late

May

early

June

late

Jun

e

Mas

s ba

sed

on A

PI s

core

s Wexford Iceland

Greenland

clutch of 3

clutch of 6

incubation with 3 eggs

incubation with 6 eggs

Figure 9.2. Estimated fortnightly median body massof adult male ( or ) and adult female ( or ) basedon field observations of abdominal profiles and theirobserved changes through the first half of the year.Graph contrasts the slow accumulation of stores atWexford (solid symbols, solid line) with the rapid ac-cumulation in Iceland (open symbols solid line) andin Greenland (solid symbols dotted line). Costs of lay-ing 3 and 6 egg clutches have been subtracted fromthe late May median values, and costs of incubationfrom these values (based on fat and protein costs fromTable 9.1). Note that this approach underestimatesbody mass at all stages because of the effects of usingfortnightly means, hence the differences in some meas-ures compared to direct mass determinations usedearlier.

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with rank. This suggests that dominant pairs werebetter at securing the best nest sites, as well asprotecting eggs and broods from predation (War-ren 1994).

The establishment of such dominance hierarchiesclearly offers a mechanism that results in asym-metric patterns of individual nutrient acquisitionin a situation where resources are limiting. Young,inexperienced birds (or those of poor quality)have low social status relative to older (or betterquality) individuals. They therefore lack both ac-cess to nutrients and the skills necessary to max-imise food intake rates, and suffer reduced fit-ness as a result. Indeed, recent evidence suggeststhat low reproductive success in early years is dueto the inexperience of paired females in food andfeeding area selection. This specifically hinderstheir ability to build up reserves in preparation fornesting (Black & Owen 1995). In that study of Bar-nacle Geese, declines in reproductive success inlater years were attributed to the male, and thoughtto be linked to declining fighting ability, whichdetermines access to optimal feeding sites for thefemale and acquisition and defence of best nestsites (Black & Owen 1995). Hence, within a pair,the ability of both individuals to maintain socialand nutrient status (of different nature) has animpact upon their reproductive success at differ-ent times throughout the duration of the pair bond.

In its recent evolutionary history, the GreenlandWhite-fronted Goose was a specialist feeder. Itexploited the highly nutrient rich overwinteringorgans of a very narrow range of species associ-ated with a rare and localised biotope (Sphagnum-filled depressions) in a geographically restrictedhabitat type (oceanic pattern mire systems re-stricted to the western fringe of Europe, chapter2). The use of such a resource also necessitates anappreciation of the periodic recovery patterns ofsuch a finite food source over more than onegrowth season. This might favour a process ofcultural learning to effectively exploit patchyfeeding resources in time (e.g. sequential exploi-tation cycles of Phleum over a few days and ofEriophorum angustifolium over at least 2 years) andspace. Seen in this historical context, a long-livedherbivorous goose species with such a highlyspecific diet would be subject to severe limitationson resource availability. This is especially the caseon the 'survival' habitat where the fitness conse-quences of food availability are potentially likelyto affect mortality as well as reproductive out-put. Selection seems highly likely to favour indi-

viduals that can maintain extended family links.These enable the youngest (and potentially themost socially inferior) birds to retain high socialrank by continued association with their parents,siblings and other kin (i.e. groups with the high-est social status). In this way, youngest birds canelevate their functional social rank and, by asso-ciation with near kin in large groups, can gainaccess to (and defend) best feeding patches. Atthe same time they gain experience and compe-tence in feeding skills, knowledge of migrationroutes and staging areas and even observe and/or assist in breeding attempts by their parents onthe nesting areas (MS11, MS12). Other groupmembers benefit from the association throughshared vigilance and food finding, and the par-ents benefit by shared vigilance in pre-nestingfeeding and in nest defence on the breeding ar-eas. In a relatively long-lived bird, the gain in so-cial status and learned experience during theyounger years might offset the loss of breedingpotential in this period, which represents an in-vestment in future breeding potential when de-parture from the family unit finally takes place.

Given that reproductive success first increasesand then declines in later years within all stud-ied goose populations (see above), this long as-sociation with kin ultimately bears a cost in for-gone reproductive output. Ultimately, the balanceof the conflict between the cost of remaining withkin versus lost reproductive output should tiptowards investment in the individual’s own re-production rather than that of kin. Only in thecase of poor quality individuals is it likely thatthe benefit of helping in the reproductive successof related birds outweighs that of pairing andleaving the family to invest in its own reproduc-tive future. Hence, at some point, a young birdmust pair up, leave the family group and effec-tively lose social rank and fall to the level of a'flock of two' in the population as whole. Thismechanism, whereby potentially the most fit, fe-cund animals must temporarily lose social statusby sacrificing their links with the dominantgroups in an attempt to breed, is apparently unu-sual amongst geese. Family break-up occurs mostfrequently during the first or second wintersamongst studied goose species. Nevertheless, ina resource-limited system, this offers a density-dependent regulatory mechanism for recruitmentof Greenland White-fronted Geese into the breed-ing population.

It is not possible to know whether the prevailing

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social system has traditionally regulated recruit-ment into the reproductive classes in the Green-land White-fronted Goose population, but it istempting to speculate this was and remains thecase. The population is characterised by unusu-ally prolonged parent-offspring relationships(25% were still associated with one parent in theirseventh winters, MS 11), even compared to otherraces of White-fronted Geese (Ely 1993). Yet theproduction of young per successfully breedingfemale (measured by family brood size on thewintering grounds) is unusually high comparedto most other goose populations, consistent withthe idea that only the highest quality pairs breedin any one year. These features are consistent witha social system that enables successful pairs tomaintain high social status through persistentassociation of earlier offspring, which seem likelyto remain with their extended families becauseof the high relative cost of pairing and losing suchstatus. Reproduction in the population as a wholetherefore involves a relatively low proportion ofthe potentially reproductively active individuals- generally only those of high quality (see Figure9.1 and 9.2 above).

Under legislative protection from shooting on thewinter quarters, the population has shown anincrease consistent with constant adult survivaland observed breeding success rates. If some den-sity dependent function were involved, wherebythe overall number of opportunities to nest in anyone year were limited to the same number everyyear, it might be expected that, above this thresh-old level, entry into the breeding class would beseverely limited. There is now some emergingevidence to suggest that such a limit exists forthe Greenland White-fronted Goose. Amongstthose wintering at Wexford and Islay (some 60%of the total population), the number of success-fully breeding pairs returning with young stead-ily increased during the 1970s, although produc-tion in any one year varied with summer tem-perature in Greenland (Figure 9.3). Since protec-tion from hunting, the absolute number of suc-cessful breeders has been stable at c.1,000 pairsin years when cold summer conditions have notlimited successful breeding (Figure 9.3). Theredoes seem therefore to be a current limit to thenumber of pairs that can breed successfullyamongst birds using these two wintering resorts(chapter 6). This is manifest amongst the markedpopulation in falling recruitment levels amongstcohorts hatched since 1984, partly a result of de-layed age of first breeding amongst this sample

but also declining brood size amongst those thatbreed (chapter 6).

The demographic data support the idea that thereis an apparent current 'ceiling' to reproductiveoutput in this population, but it is far from clearhow this limitation is exercised. There might be alimit to the extent of breeding habitat or numberof nest sites, but these seem highly unlikely, giventhe wide extent of available habitat (chapter 6).Furthermore, the limit could be to brood rearingnursery habitat, or to the post fledging survivalof young. Both of these factors also seem highlyunlikely, given that a density dependent mecha-nism would tend to reduce brood size (for exam-ple, as a result of losses of smallest goslings Owen& Black 1989), rather than result in a loss of entirebroods from the population. In the GreenlandWhitefront, a characteristically low proportion ofsuccessful breeders return with unusually largefamilies compared to other geese populations.

Hence, it would therefore appear that relativelyfew pairs attempt to breed in any one year, andamongst those pairs which do, the majority breedsuccessfully, in terms of raising large numbers ofyoung per family that survive to reach the win-tering grounds. As discussed above, this couldbe the result of density-dependent limitation inaccess to nutrient acquisition on the winteringgrounds, the Iceland spring staging areas, inGreenland during pre-nesting feeding or a com-bination of all three. Since the extended familyrelationships persist on the wintering, spring stag-

0

200

400

600

800

1000

1200

1965 1970 1975 1980 1985 1990 1995 2000Num

ber

of s

ucce

ssfu

l bre

edin

g pa

irs a

t Is

lay

and

Wex

ford

com

bine

d

cool springs

mild springs

Figure 9.3. Total number of successfully breeding pairs(i.e. parents returning with at least one young) in au-tumn from Islay and Wexford combined. Open sym-bols are years with cooler than average June tempera-ture in West Greenland, solid symbols warmer thanaverage (based on data from Zöckler & Lysenko (2000).Note the apparent constant maximum number of suc-cessful breeding pairs since protection (arrow) in sea-sons of above average summers.

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ing and (to a lesser known extent) pre-breedingareas, it seems likely that a brood female with at-tendant offspring from previous years obtainsconsiderable advantages for nutrient acquisitionduring all three phases of the prelude to breed-ing. Furthermore, the association of offspringfrom previous years could potentially enhance nestdefence and protection of subsequent hatchedyoung. In contrast, lone pairs face considerabledisadvantages owing to their low social status,which denies them access to the best feeding op-portunities. They must increase food intake ratesto compensate for loss of access to richest foodpatches by consuming higher quantities of lowerquality foods to meet threshold levels of storesneeded to attempt reproduction. Even after lay-ing a clutch, the lone pair lacks kin associates fornest defence from predators.

It therefore seems most likely that there is a limitto individuals entering the breeding class and thislimitation is likely to be condition based. It is al-ready known that pre-nesting feeding areas arespatially limited in spring and patterns of snow-melt could impose further limits on food avail-ability (see Glahder 1999). Hence, pre-nestingspring food availability is likely to specificallylimit resources available to potential brood fe-males. Only those individuals most efficient atnutrient accumulation in the period up to and im-mediately after arrival in Greenland can achievethe necessary stores for successful reproduction.

9.2 The impact of hunting mortality

In the absence of histories of individually markedbirds from the years when hunting occurred inall seasons, it is impossible to determine the trueeffects of winter hunting mortality on GreenlandWhite-fronted Geese. The comparison betweenHaldane estimates of survival before and afterprotection suggests hunting was additive. Thesimple modelling exercise included here (chap-ter 8) gives some support to the hypothesis thatcompletely additive hunting mortality at Wexfordwould explain the period of stable numbers dur-ing 1969-1982, and the observed rate of increaseafter protection. However, in the two years whenhunting was permitted on the Wexford Slobs since1982, there was no convincing difference in an-nual adult or juvenile survival based on resight-ings of individually marked birds.

However, the unusually high mortality in one

year (1989) which resulted in 75% mortalityamongst young and reduced adult survival dem-onstrates the sensitivity of the population to suchoccasional stochastic events, and their impact onsubsequent population trends. As previouslydemonstrated, the population is highly sensitiveto small changes in annual adult survival rates(Pettifor et al. 1999), and therefore, it is not sur-prising that the removal of winter hunting hadan immediate effect on population trajectory.Given this direct impact of changes in survivalrate on change in population size, it does appearthat protection from hunting was the cause of theincrease in numbers in the population after 1982.The site-safeguard programmes of the last 20years have only contributed in so far as protec-tion of regularly used roost sites and other pro-tected areas have guaranteed their perpetuation.

An interesting feature of the relationship shownin Figure 9.3 is the apparent 'jump' in the numberof successful pairs which returned to Islay andWexford in warm summers following protectionfrom hunting on the wintering grounds. Thereseem some grounds for believing that the levelsof recruitment amongst these wintering elementsof the population increased rapidly to the current(apparently limited) level immediately followingcessation of hunting. In the absence of resightinghistories of individually marked birds before andafter protection, it is impossible to explain thisphenomenon in terms of individual behaviour.Nevertheless, it is interesting to speculate as towhether hunting has an effect on reproductivesuccess in the population as well as a direct effecton adult annual survival. Such a relationshipcould be the result of the effects of wildfowlingdisturbance to geese, known to affect breedingsuccess in some populations (Madsen 1995).However, it is also clear from observations on thewintering grounds that extended families tend tofly in small unattached groups, whilst non-breed-ing elements of the population aggregate intolarge flocks (unpublished data). Hence, althoughfamilies form a very small proportion of the over-all population, their potential frequency of en-counter by a hunter is disproportionately high.Observations of behaviour of wildfowlers hunt-ing Pink-footed Geese in west Jutland, Denmarkhave shown that hunters tend to shoot at indi-vidual goose flocks as these are encountered. Inthat study, family groups were more likely to beshot at than large flocks of geese not because oftheir numerical abundance, but simply becauseof their greater frequency of encounter with hunt-

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ers (J. Madsen unpubl. data). In this way,wildfowling could potentially select for the ex-perienced breeding adult element of the popula-tion, even though these individuals are numeri-cally few amongst Greenland White-frontedGeese. Hence, through the death, or sub-lethalcrippling of one or both partners of an experi-enced pair, the most productive element of thepotentially breeding population is being lost bybreak up or total loss of successfully breedingpairs. Although there are no data to support suchan assertion, this would provide some explana-tion for the secondary effect of the cessation ofwinter hunting on the increased reproductiveoutput of the population since the early 1980s. Itwould be essential, should winter hunting everbe reinstated in this population, to at least moni-tor these secondary effects on the population dy-namics of the race, in addition to tracking the di-rect effects on annual survival rates.

At present, we can say little about the effects ofthe continuing kill of some 3,000 birds in Icelandon autumn migration every year, but it is clearthat removal of this number of birds has notstopped the increase in the population over thelast 25 years.

9.3 Current conservation issues ofconcern

It would therefore seem that the population wasrestored to favourable conservation status by sim-ple legislative manipulation of human-inducedmortality processes. Restrictions on hunting haveundoubtedly restored this population to a morefavourable conservation status since 1982, mostnotably at Wexford and Islay, where a direct ef-fect can be demonstrated. However, amongst thenumbers wintering elsewhere in Britain, flockscontinue to decline and disappear. Having re-versed the overall decline in the population, thenext priority is to identify factors affecting thecontinuing declines and extinctions that are oc-curring at wintering areas other than the majorsites. This is necessary in order to achieve thedeclared aim of maintaining the current geo-graphical range of the population.

A variety of land-use changes have been takingplace since the early 1980s in Britain and Ireland.In the 1980s and 1990s, intensification of grass-land management (especially on Islay) resultedin many birds wintering there moving to feed on

new rotational grass leys. This might have re-sulted in geese retaining higher levels of nutrientand energy stores throughout the winter periodthan would have been possible on more tradi-tional natural and semi-natural habitats. This inturn brought Greenland White-fronted Geese intolocal conflict with agriculture (including shoot-ing mortality permitted under licence). Now, withthe cessation of dairying on Islay in 2000, there isthe prospect of wide scale changes in grasslandmanagement on that island, this time involvingreduction in levels of management intensity insome areas. In addition, many of the outlyingflocks in Scotland and Ireland were affected bythe general decline in the rural economy, with theresult that low intensity agricultural land has be-come abandoned or neglected in recent years.Hence, away from the large concentrations, geeseare facing habitat loss and degradation.

Even at Wexford Slobs, there have been substan-tial changes in land use in the last 50 years. Thiswas initially through improvements to grasslandmanagement techniques, but in the last two dec-ades due to increasing tillage (including cultiva-tion of crops such as carrots, maize and linseed)and even forestry on the South Slob (now largelylost as a goose feeding resort in very recent years).Hence, the geese have faced a range of differentchanges to land use at wintering resorts over dif-fering time scales. Can we learn anything fromthe historical perspective regarding goose re-sponses to changes in agricultural practice? Giventhe competition from Canada Geese and/or glo-bal climate change look set to affect the popula-tion adversely through impacts on the breedinggrounds, what mitigation measures on the win-tering areas might be possible or appropriate toreverse these trends?

There is considerable evidence to suggest that theflocks declining most rapidly are those with thefewest and least extensive feeding areas (MS14).Although a link has never been demonstrated, itseems likely that these sites are the most suscep-tible to disturbance by humans, since their re-stricted winter range limits escape options toundisturbed areas (Norriss & Wilson 1988). It isimportant to determine for those flocks whetherthe changes in number are due to changes in de-mography (i.e. low survival and/or fecundity) orpatterns of immigration and emigration. Al-though there have been many studies of the ef-fects of disturbance on birds (e.g. affecting spa-tial distribution, Madsen & Fox 1995, Fox &

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Madsen 1997, Madsen 1998), demonstrating im-pacts at the population level have proved moredifficult (Madsen 1995). If it is possible to estab-lish such links, it becomes more possible to ad-dress the causal factors, identify the points in thelife cycle at which these factors operate and im-plement management to mitigate such factors.Does poor feeding opportunities and/or distur-bance directly affect survival or breeding success,and what are the proximate causes? It is well dem-onstrated that disruption to feeding patterns onspring staging areas prior to migration to breed-ing areas affects the reproductive potential ofgeese (Madsen 1995), but what of disturbance atother times of year?

Given the relative slow build up in body storesthroughout the winter in this population, it mayseem less likely that disturbance in mid-wintercould affect departure condition than during thespring pre-departure phase. In comparing be-tween individuals, Figure 9.1 shows graphicallyhow reduced rates of mass accumulation couldresult in longer term fitness consequences, butsuch a model could equally apply between sites.Where nutrient and energy acquisition is reducedrelative to best feeding opportunities, the poten-tial to attain store thresholds at staging areas laterin the annual cycle is diminished. Birds depart-ing from poor quality or highly disturbed win-tering areas may not be able to compensate in Ice-land and Greenland, and hence may suffer reducedfitness as a consequence. Indeed, if the numbersof geese wintering on high quality habitats in-creases, and these birds depart in good condition,birds departing in poor condition from winteringareas are likely to face even greater competition inspring if food resources in Iceland and Greenlandare limited. Hence, a mechanism of intra-specificcompetition operating away from the winteringareas may actually be influencing the relativechanges in abundance of Greenland White-frontedGeese at different wintering resorts.

Climate change may play a role at several stagesin the life cycle of the geese. There is a trendamongst Greenland White-fronted Geese for themost southern wintering flocks to show the mostdramatic declines (MS14). The recent declines atWexford are attributable to falling fecundity atthat site at least, but does this hold for other win-tering flocks in the south of Ireland showing simi-lar trends? Is this reduction in breeding becauseof global climate change affecting their breedingconditions in the north of their west Greenland

range? Or could it be that the same climate changeis affecting the phenology of growth of food plantsexploited in spring on the wintering areas andstaging grounds in Iceland? Could the springflush of grass production in southern Ireland (theso-called “spring bite”) be occurring earlier andearlier as a result of climate change, that it occurstoo soon for geese to effectively exploit? A fullexploration of the weather archive needs to beundertaken before we can answer such questions.Furthermore, the patterns of change in goosenumbers at different wintering resorts need to beinvestigated in terms of their demography anddistribution, before it is possible to identify whatenvironmental factors are likely to shape theseprocesses.

In many areas of the summering grounds, White-fronted Geese follow the phenology of thaw inthe west Greenland landscape. This involves theexploitation of plants in the early stages of growthas they are released from dormancy by the thaw,but before the onset of rapid growth. On a macroscale, this involves a movement up-hill follow-ing the general amelioration of temperature as thespring and summer progress. Later in the season,at high altitudes, this pattern reflects aspect andtopography, with the geese essentially followingthe disappearance of late lying snow patches,which offer the last burst of plant production inthe landscape. The geese especially exploit thisphenology of plant growth during the moult,when their ability to switch between habitats isseverely limited by their association with waterbodies to which they resort when threatened bypredators. The proximity of late snow patches inassociation with open water therefore limits avail-able moult habitat in many areas and the timingof melt of these areas may be critical to theregrowth of flight feathers at this time. Changesto patterns of melt and hence the phenology ofplant growth at different altitudes could there-fore have consequences for the feeding efficiencyof geese throughout the summer.

And what of the effects of competition from Can-ada Geese on the summering areas? Accumulat-ing evidence suggests exclusion of White-frontedGeese from formerly occupied moult sites. Ifmaintained, this represents net Whitefront habi-tat loss. If available moulting habitat is in any waylimited, this will ultimately have some effect onthe population as a whole, as long as the num-bers of Canada Geese continue to increase. Thisrepresents yet another dimension to population

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limitation which operates during another stage ofthe life cycle, until now relatively little studied.

9.4 Overview and future research

The freedom to fly gives long distance migratorybirds the opportunity to exploit distant nutrientand energy sources in the course of their annualcycle. In particular, given endogenous sources ofenergy to sustain periods of flight, it enables or-ganisms to move between islands of abundantfood resources across large expanses of whollyunsuitable habitat. At the same time, this verymobility creates patterns of energy and nutrientdemands in the form of expensive migratorycosts, met from storage accumulated during timesof resource abundance. The synthesis presentedhere is helpful in conceptualising the annual cy-cle of the Greenland White-fronted Goose as a se-quence of discrete periods according to energy/nutrient acquisition or demand. Typically, this re-lates to periods of storage of energy and/or nu-trients followed by short bursts of use of accu-

mulated stores (generally breeding events or mi-gration episodes). However, there are also peri-ods in the life cycle where extra demands (suchas wing moult, or defence of body condition inearly to mid-winter) can be met by exogenoussupply (Figure 9.4).

It has frequently been asserted that evolution hasminimised the overlap of energy- and nutrient-demanding periods of the life cycle of birds (the“staggered costs” hypothesis coined by Lovvorn& Barzen 1988). In the Greenland White-frontedGoose, this separation in time and space offersthe possibility to specifically identify critical pe-riods in the annual cycle. In this way, it is possi-ble to assess the ability of individuals to reachcritical condition thresholds in order to meet eachof the specific demands they face in discrete peri-ods within the annual cycle.

From the nature conservation and research stand-point, such an opportunity is fortunate in offer-ing a framework by which to concentrate futurestudy efforts. For each period of accumulation of

Figure 9.4. The annual cycle of an adult breeding female Greenland White-fronted Goose represented as asequence of discrete calendar events, categorised as a series of periods of energy/nutrient acquisition or de-mand. These generally fall into three categories: (i) Periods of storage of energy and/or nutrients (shown cross-hatched in the bars above). (ii) Use of accumulated stores (generally breeding events or migration episodes,shown as dark bars). (iii) Periods in the life cycle where extra demands can apparently be met by exogenoussupply (such as during wing moult, brood rearing or the defence of body condition in early to mid-winter,shown as shaded bars). Note that the period of brood rearing also represents a critical period for the female,during which she must recoup depleted stores and potentially reserves utilised during brood laying and incu-bation.

Winter accumulation of stores

Spring migration to Iceland

Accumulation of stores in Iceland

Spring migration to Greenland

Accumulation of stores in Greenland

Egg laying

Incubation

Brood rearing

Wing moult

Accumulationof stores in Greenland

Autumn migration to Iceland

Accumulation of stores in Iceland

Autumn migration to wintering grounds

Winter maintenance

J F M A M J J A S O N D

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stores, the rate of acquisition (and hence condi-tion state by a given time) will be affected by arange of factors acting on the individual. For in-stance, on the wintering grounds, the level towhich an individual can maintain suitable foodintake rates in relation to maintenance expendi-ture is affected by primary external factors (suchas food quality or abundance). This is then modi-fied by secondary factors (such as rates of dis-ruption to feeding patterns through human dis-turbance or intra-specific interference). If we as-sume that the foraging ability of an individual isrelated to its ability to accumulate stores in an-ticipation of energetic expenditure, in the shortterm we can use measures of feeding efficiencyand/or rates of change in individual conditionto contrast the relative costs and benefits of dif-fering foraging situations. Such a comparativeapproach based on detailed observations ofmarked individuals offers the opportunity to con-trast, for instance, the ability of individuals ofdifferent status to accumulate stores in the pres-ence/absence of disturbance (Madsen 1995). Itbecomes possible to compare rates of change inbody condition based on feeding on differenthabitat types, or examine differences in birds ofdifferent social rank. Viewed over longer timescales, the short term ability to maximise effi-ciency in store accumulation ensures not only thesurvival of the individual but ultimately the re-cruitment and lifetime reproductive output of theindividual. Based on the accumulated life histo-ries of individuals, we can contrast differences inlifetime reproductive output as a fitness measureof the different strategies used by individualsthroughout their lives.

On-going studies have already demonstrated theability to detect differences in energy accumula-tion rates between Greenland White-frontedGeese using different grass swards during springstaging at the same site in Iceland (Nyegaard etal. 2001). From observations of collared individu-als, it is known that different individuals exploitdifferent sward types, many showing consistentpatterns between years (chapter 4). This (not un-expectedly) appears to influence the rate ofchange in abdominal profile scores of individualgeese exploiting different sward types (MS18 andunpublished data). The accumulation of moreindividual life histories with details of habitat use,patterns of store acquisition and condition ondeparture from Iceland will enable the assessmentof the fitness consequences from such foragingbehaviour in the fullness of time. These linkages

between different elements in the life cycle areessential if we are to obtain a deeper understand-ing of how individuals perform in terms of sur-vival and reproduction measures with regard tothe environment they exploit.

There are thus 3 measures available to assess in-dividual performance: the balance of food intakerate versus use over short periods, the rate of ac-cumulation of stores for completion of demand-ing episodes in the life cycle and ultimately thesurvival and reproductive output of the indi-vidual. It is possible to combine specific detailedinvestigation of these elements with the longerterm historical resighting data, which providerecords of how an individual has performedthroughout its life. For geese ringed as goslingsin their first winter, these records include whichareas and habitats they exploited at different timesof the year, when they separated from parents,how often a bird has changed wintering site, howoften it returned to wintering areas with youngand how long it lived. What is interesting is tosee how individual decision-making can affectfeeding efficiency, condition and, ultimately, fit-ness. Although Greenland White-fronted Geeseare highly site loyal, birds do change winteringsites (MS9). In chapter 4, we saw how individualbirds tend to specialise on a particular grass swardduring staging in Iceland in spring, but some birdsdo show the ability to change from less nutritiousswards to more profitable ones (Figure 4.9).Hence, individual decision-making enables modi-fications to feeding efficiency, condition and fit-ness, and it is the consequences of these decisionswhich offer insight into how individuals behaveand how this contributes to overall populationbehaviour (Figure 9.5). Combinations of histori-cal data and new investigations enable use ofthese measures to assess factors affecting indi-vidual breeding success and survival and an at-tempt is made to set out the major research objec-tives in Appendix 2.

The priorities for the immediate future are to con-tinue to monitor the patterns in numbers and dis-tribution which is only possible on the winteringareas (see Appendix 2 for details). The individualmarking programme at Wexford must continueif we are to be in a position to interpret the changesin numbers based upon the count information.This programme should be extended to more in-dividual marking and monitoring at other sitesto construct the basis for comparative studies dis-cussed in greater depth below. The basic ration-

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ale for all research to date has been driven bynature conservation objectives, and althoughthere are many curiosity driven research objec-tives that could be included as well, the key con-servation questions are as follows: (i) What fac-tors affect changes in abundance at winteringsites? (ii) What factors limit successful recruitmentinto the breeding class? (iii) How will the effectsof predicted global climate change affect thepopulation (iv) How will the Canada Goosepopulation of West Greenland affect the White-fronted Goose population?

Armed with a means of measuring condition, itbecomes possible to reformulate these questionsin the context of the direct effects of food qualityand factors affecting feeding rates (as a result ofclimate change, inter- or intra-specific competi-tion or human disturbance). Such an approach canoffer conservation management solutions on thewintering grounds (for example where interven-tion management can improve food quality orrestriction on human activity can reduce distur-bance to feeding patterns). Using measures ofcondition on the pre-breeding spring staging ar-eas, it becomes possible to measure and contrastdensity-dependent effects amongst potentiallybreeding females in the prelude to clutch initia-tion and investigate the role of nutrient limita-tion and effects of competition at this time.

Such empirical relationships are vital for our un-derstanding of small-scale population processesand individual behaviours. However, there re-mains a need to generate large-scale predictionsabout the effects of, for instance, macro changesin land use on the wintering grounds, or the ef-fects of climate change throughout the entire geo-graphical range. From the point of view of con-tributing to predictive models, such investiga-tions also provide basic data regarding the be-haviour of individuals in response to local goosedensities or their position in dominance hierar-chies. When does a goose of potential breedingage pair and how is this decision condition me-diated? What conditions make an established pairemigrate from a poor quality winter site to an-other site? What are the fitness consequences ofchanging site for low, medium or high rankingbirds at wintering sites of different quality?

Perhaps most important, the measure of the ca-pacity of individuals to make adjustments to theirannual cycle which potentially improve fitnessmeasures gives the potential to assess the flex-ibility of the population and its capacity to ex-ploit novel opportunities. This element is impor-tant. In the past, it has been difficult to predictthe patterns of development in the abundance ofwild goose populations. From the low levels ofabundance in the 1930s, protection measures put

NUTRIENT & ENERGY

ACCUMULATIONRATES

CONDITIONability to meet

current and future nutrient

and energy needs

FITNESSCONSEQUENCES

RESEARCH1. Determining factors

affecting food availability to an individual, influenced by

site based disturbance, range quality, local density,

position in dominance hierarchy, etc.

OBJECTIVEA. Predicting effects of change likely to come from climate, land-use

policy and conservation management change

RESEARCH2. Monitor the processes of

individual decision-making which affect nutrient acquisition, e.g.

emigration from poor quality sites, pairing and departure from family

unit

OBJECTIVEB. Establish the behavioural flexibility of the individual to change its ability to acquire

adequate stores to attain condition thresholds at critical

points in the life cycle

Individualdecision-making

RESEARCH3. Measure individual condition

at all stages of the life cycle, especially during transition states (when individuals go

from phases of accumulation to expenditure)

OBJECTIVEC. Establish the effects of

individual behaviour on the accumulation of stores for

critical periods of use in the annual cycle

RESEARCH4. Determine reproductive and survival consequences for the individual of nutrient/energy

accumulation and scale up to population processes

OBJECTIVED. Predict future individual

behaviour and potential future population trajectories

Figure 9.5. Schematic representation of the effects of nutrient accumulation rates (mediated by individual be-haviour) on body condition and fitness in Greenland White-fronted Geese, showing associated research ques-tions and objectives associated with each level.

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in place from the late 1940s onwards in the UnitedKingdom ensured the increase in goose numbersto the present day. However, the numbers of sev-eral populations stabilised in the 1970s and 1980s,generally thought associated with density de-pendence (e.g. Figure 1 in Pettifor et al. 2000).Largely unseen from the perspective of the win-tering grounds, Pink-footed Geese nesting in Ice-land and Barnacle Geese in Svalbard expandedto new colonies, and showed renewed periods ofincrease that could not be predicted on the basisof population-based models constructed usingdemographic data from previous years.

It is often extremely difficult to determine thestrengths of density dependence in empiricalstudies (e.g. Pollard et al. 1987). Historical popu-lation data are likely to be collected over a verynarrow range of population sizes and environ-mental conditions, unlikely to offer the basis forrobust predictions for the future (see discussionin Pettifor et al. 2000). For this reason, it has beenargued that models predicting the response of apopulation to environmental change need to bebased upon the aggregative total of individualbehaviours (Goss-Custard 1985, Goss-Custard &Durell 1990). In this way, models can be devel-oped to predict effects of change in the environ-ment on a population based on the cumulativesum of individual responses under novel circum-stances. Such models have been developed us-ing game theory to explore how individuals ofvarying competitive ability can exploit a patchyand variable food supply. The classic models havebeen built based upon maximising individual fit-ness in Oystercatcher populations, by Goss-Cus-tard and co-workers at individual site (Goss-Cus-tard et al. 1995a,b) and at population levels (Goss-Custard et al. 1995c,d). Such models need to belarge scale and encompass the entire annual cy-cle, as exemplified by the application of Pettiforet al (2000) to other goose populations. The appli-cation of such models to the Greenland White-fronted Goose would identify the key model pa-rameters required and could prove extremelyimportant to our understanding of future poten-tial change.

9.4 Conclusions

There is accumulating evidence to suggest thatduring the latter half of the 19th Century, theGreenland White-fronted Goose began a shift inhabitat use from very limited small-scale habitat

types to emerging (and far less geographicallyrestricted) agricultural habitats. Nevertheless, thepopulation has continued to be geographicallyrestricted by virtue of its winter site fidelity, andcontinues to probe for the underground storageparts of plants (bulbils, stolons, rhizomes, etc.),even in current agricultural landscapes, far morethan other western European goose populations.Greenland White-fronted Geese appear behav-iourally constrained by inherent site fidelity anda general conservatism with respect to the exploi-tation of novel habitats. Only one small new win-tering flock is known to have become establishedin the last 25 years (MS14). Although geese haveshown shifts from natural and semi-natural feed-ing habitats to managed grasslands, these haveonly occurred when these grasslands are createdin close proximity to existing feeding areas. Whilethere are abundant areas of such grasslands avail-able throughout Scotland and Ireland, currentlyunexploited by Greenland White-fronted Geese,there are no signs of colonisation of such suitablehabitat away from traditionally used roost sites.Hence while the potential for extensive spread ofthe population looks possible, the capacity of thepopulation to do so has been limited to in-fillingin close proximity to existing home ranges ex-ploited by the current wintering flocks.

Assuming that this site fidelity holds for otherperiods of the life cycle, its potential breeding,staging and wintering range is geographicallylimited. This inevitably limits the potential car-rying capacity of the habitat globally and is likely,at some stage, to lead to an eventual limitationon total population size. Nevertheless, as we haveseen, different habitats have the potential to limitpopulation change in different ways, and to re-turn to the ideas of Alerstam and Högstedt, thesecan be divided into 'breeding' and 'survival' habi-tats, where such factors may operate. Hence, wecan conceive of winter, spring staging and pre-breeding habitats as comprising the 'breeding'habitat in so far as any or all could potentiallylimit reproductive output in the population as awhole. Equally, we could conceive of 'survival'habitat including the moulting areas in Green-land, since the successful regrowth of flight feath-ers is essential for flight, to enable movement be-tween all the geographical areas used by geese intheir completion of the annual cycle.

Hence, breeding and survival habitats and the lifecycle processes completed in these habitats arenot necessarily limited to breeding and non-

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breeding geographical locations respectively.Critical elements in the annual cycle can occur atdifferent places in time and space, and accord-ingly factors that regulate the rate of change orlimit population size can affect population dy-namics in different places at different times. Inthe case of the Greenland White-fronted Goose,we begin to see that different mechanisms havelimited the size of the population in the very re-cent past. This has either been through the main-tenance of low (relative to potential) annual sur-vival rates through hunting on the winteringgrounds, or through recent declines in fecunditydue to apparent restrictions of entry to breedingage class (potentially through restrictions on pre-breeding condition of females). Hence, we haveseen a population that was maintained at a levelbelow its potential by hunting kill expand in re-sponse to protection from winter hunting. Thepresent rate of population increase shows signsof slowing in the last few years, despite no de-crease in annual adult survival, showing thatsome other mechanism is responsible. This is dueto falling fecundity, with a stable number of breed-ing pairs returning to wintering grounds withyoung despite increasing population size. At onewintering site, Wexford, this trend has ultimatelyresulted in a decline in wintering numbers. Thismay to some extent be the result of a run of sum-mers with low June temperatures. This may inturn be a consequence of global climate changethat has made, and is predicted to continue tomake, summers in northern west Greenlandcooler in coming years. Hence this trend may be-come manifest elsewhere if patterns of climatechange continue as predicted.

The conservation message from this type of studyis clear. We need to be able to understand the roleof different processes throughout the annual cy-cle of such populations and we need to be able tomonitor these processes and their effects. It isimportant to be able to establish which factorsaffect a population in which ways and at whichperiods in the annual life cycle. It is not enoughto establish patterns in survival and reproductionat one wintering site and expect to be able to un-derstand the processes that shape the changes intotal numbers from year to year. Although it ispossible to make some inferences about the pat-terns of population change, as is evident here, itis not yet possible to demonstrate causal relation-ships. Conservation needs more examples ofexperimental manipulation of legislation and theirdemographic repercussions on population change,

in order to be more confident in predicting theeffects of change. In fact, there exist very few goodexamples of this (see Nelson & Bartonek 1990).In North America, the implementation of adap-tive waterfowl management strategies ('wildlifemanagement by experimentation', MacNab 1983)has met with mixed success (Johnson & Williams1999). One major problem with, for example, at-taining the objective of determining the effects ofhunting harvest on annual survival has been theconflict between maximising the hunt harvest andmaximising the knowledge derived from experi-mental manipulation of the hunting bag. Never-theless, it is essential to understand the strengthof such processes, including, for example, thestrength of density dependence and the extent towhich differences in individual behaviour deter-mines the access of individuals to necessary nu-trients. It is also necessary to demonstrate theextent to which hunting mortality is additive. Ifit can be demonstrated that hunting mortality ispartially compensatory, sustainable hunting canbe maintained below a critical threshold withoutseriously reducing total population size.

All these effects require monitoring of change innumbers in the population as a whole, whetherthis is achieved through annual winter census (in-cluding proportions of young present to estab-lish breeding success and, by difference, survival),or surveys of the pre-breeding, nesting or moult-ing areas. It is essential that at least winter inven-tories and measures of breeding success are main-tained, as these remain the only practicable meansof monitoring the numbers and breeding/sur-vival processes in the population. Although it isdifficult to maintain count coverage by observersin remote areas (where conditions may be logis-tically difficult), this remains the absolute prior-ity to extend the present time series. At the mo-ment, there are no attempts to carry out regularaerial survey of spring staging, nesting and moult-ing areas in Greenland, although all have beencarried out on a limited basis in the past. Thesethree periods are, as we have seen, critical onesin the annual life cycle and regular (e.g. every fiveyears) survey of these would be highly desirable.Such information might provide great insightsinto the way local conditions (including localgoose densities) may affect dispersal, survival andreproduction.

Nevertheless, if we are ever to be in a position tointerpret the reasons behind observed changes inpopulation changes, we must continue with the

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study of the behaviour of marked individuals. Wecan use capture-mark-recapture programmes toestimate survival, follow reproduction, measurerates of individual emigration/immigration fromwintering sites and determine individual life-timereproductive success and dispersal patternswhich offer insights into how changes at thepopulation level are manifest. Such informationis vital if we are to understand the changes atpopulation level and determine how density af-fects the individual, in terms of recruitment andsurvival probabilities, with respect to individualquality. Since populations are composed of indi-viduals of differing quality, it is important to beable to show how competitive ability, age, expe-rience and social status of the individual affectfood intake rates, store acquisition and ultimatelyfitness measures. Greenland White-fronted Geeseare long lived and may take six or more years toenter breeding age classes. For this reason, it isincreasingly important to mark a representativesample of individuals on a regular basis overmany years, to generate resightings of individu-als and contribute to life histories that establishasymmetry in dispersal, fecundity and survivalwith regard to specific behavioural traits. In par-ticular, it is increasingly important to maintain apool of marked birds to form the basis for studiesof differences in nutrient acquisition throughoutthe annual cycle. There have been no specific be-havioural or energetic investigations relating tothe effects of social status and age on access tobest quality food patches, peck rate and generallevels of nutrient and energy acquisition. The rela-tively large numbers of marked individuals in thispopulation, together with their extreme site loy-alty, offer exciting possibilities in this respect. Itis not enough to suggest that dominance hierar-chies potentially skew the ability of an individualto acquire body stores, there needs to be somedirect evidence of how and why this is achieved.

The lack of detailed information relating to geesefrom this population wintering away from Wex-ford is lamentable. Given the difference in demo-graphic patterns between Wexford and Islay, itwould be highly desirable to resume a pro-gramme of regular capture-mark-recapture of in-dividuals on Islay, preferably through a pro-gramme of collar marking in parallel to those atWexford. Catching throughout the season at othersites would generate data on seasonality of mass

changes at other resorts for comparison with thepattern from Wexford. We need to learn moreabout the habitat use and other factors affectingnumbers at lesser winter resorts, especially thosethat give immediate concern for their well being.At present, we do not know if the declines at suchsites are due to poor survival, low reproductivesuccess, high emigration, low immigration or acombination of some or all of these factors. Again,it is important to establish the causes of thesechanges before it is possible to tackle the conser-vation challenge through implementation of man-agement action.

Finally, having identified the key elements thatpotentially influence survival rates and fecundity,it is essential to test these in the field to establishsome level of causation. Is climate change driv-ing the difference in reproductive output at Wex-ford and Islay? Both wintering aggregations areshowing declines in individual female fecundity,but this is greater at Wexford, where the effecthas been to cause an overall decline in numbersnot attributable to increases in the balance ofemigration/immigration, nor to changes in an-nual survival. Is this because of changes in habi-tat at Wexford, cooler summers on the more north-erly breeding areas which Wexford birds tend touse, or a combination of these factors? We needsimultaneous studies of reproductive output fromdifferent parts of the breeding grounds with re-spect to local meteorological conditions from anumber of years to establish the trends and pat-terns in breeding success. This would provide afirmer platform for predictions of the effects ofglobal climate change than is possible at present,and enable generation of population predictionsfor changing scenarios as global climate modelsimprove. We also need to understand how den-sity dependence is manifest through dominancehierarchies – what are the real costs and benefitsto an individual (e.g. in terms of fat or proteinaccumulation rates) of being part of a large group,or situated at the bottom of the league of socialstatus? We need to be able to quantify these rela-tive costs and benefits before we can be in a posi-tion to understand the function of such status andthe strength of its effect in terms of fitness conse-quences for individuals. Only by understandingthe behaviour of the individual will we be in aposition to predict the future behaviour of theentire population.

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A thesis is supposed to be primarily the work ofa single individual, but all the happy experiencesrecounted here would simply not have been pos-sible without the enormous help and support ofa huge number of people. It is invidious to listfolk as if to rank to assistance, but there are somany I would wish to acknowledge. First andforemost, I would like to thank my parents forindulging their son and allowing him to pursuehis often rather eccentric interests, the freedomto explore has given me great pleasure ever since.My family, especially my wife Anne, but latterlyalso Gwen and Mia, have been enormously tol-erant in my absence, yet so welcoming on everyhome coming – I could have achieved nothingwithout their support throughout. At university,Andrew Agnew, an inspirational character whoinfluenced so many graduates of our day, ignitedmy interest in the glorious but frustrating field ofecology into full flame. It was he more than any-one who proved to us we could achieve the im-possible, and many of us owe him a tremendousdebt. It was Will and Alison Higgs, however, whoturned the dream of an expedition to Greenlandinto the reality of 1979, and to them we all areespecially grateful for everything that has flowedsince. My thanks also to David Stroud, withwhom it continues to be a great privilege to work.David is one of the great “backroom boffins” whohas steered nature conservation through thestormy waters of the 1990s, but to see him comealive in the field is to be reminded of the cost toresearch of his enormous personal commitmentto conservation. It has been a great experience towork with David over many years and I am in-debted to him for so much constructive help andflow of great ideas and discussions, many ofwhich are presented here. His detailed commentsupon an earlier draft were a tremendous boost.They reminded me what an adventure it had beento work together in the early days. I owe a tre-mendous personal debt to Hugh Boyd, who in1979 placed enormous faith in a ragged band ofundergraduates, the fledgling Greenland White-fronted Goose Study and to our continuing sur-prise has (apparently) been taking us seriouslyever since. It is impossible to describe the influ-ence Hugh has had upon my life, and he contin-ues to be there whenever needed, for which I havenever been adequately able to express my grati-tude, either in word or deed. Hugh was even pa-

tient and kind enough to read this entire thesisseveral times and offer constructive and highlystimulating comments. His transatlantic perspec-tive and great patience with incompetence is im-measurable and he continues to stimulate, opendoors and cross-fertilise for us all. For this I amespecially extremely grateful. We met Hughthanks to the good offices of Sir Peter Scott whowas also gracious enough to understand our en-thusiasm when we started our studies. His influ-ence remains tangible almost every day, and I wasvery grateful to him for the opportunity to con-tribute to his work at the Wildfowl Trust, latterlythe Wildfowl and Wetlands Trust. I must also ex-press my deep gratitude to Henning Noer, whonot only engineered the unlikely prospect of myworking at Kalø in Denmark, but was also respon-sible for finding me time in my work plan to com-pile this thesis. I sincerely hope that its produc-tion will provide some satisfaction and stimulusthat he, too, will one day deliver his own dispotat!

Although never the major subject of investigation,the study of Greenland White-fronted Geese hasbeen supported financially by a huge number ofpeople and institutions. I would especially liketo thank all the people who privately supportedour expeditions to Greenland, and all the adoptersof ringed birds who enthusiastically followed thesubsequent movements of geese marked inGreenland. Acknowledgements of the majorsources of financial support given to projects inrecent years are given in the accompanying pa-pers. However, I would especially thank the Wild-fowl & Wetlands Trust and the Danish NationalEnvironmental Research Institute for their com-mitment and for supporting this work whilst intheir employ over the years. The Irish NationalParks & Wildlife Service were kind enough tofund a review of the research programme in 1990,which funded Stephanie Warren’s work at thattime, but I gratefully acknowledge their supportin many different ways over many years.

Indeed, looking back on so many happy timesspent in Ireland, it is with much warmth that Ienjoy the friendship of many there. I must singleout Alyn Walsh for his companionship and skillon so many catching expeditions and so manyhappy hours in the field. His family, Alice andOran, have also been so welcoming and kind

10 Acknowledgements

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whenever we have invaded their house at Wex-ford Slobs. Very fond thanks to them and to JohnWilson who was the mastermind behind the en-tire Greenland White-fronted Goose collar-mark-ing scheme. John has been the quiet, but deter-mined, driving force behind the enormous Irishcontribution to Greenland White-fronted Gooseresearch and conservation. It is he who has en-sured the active collaboration of all parties thathas made the work recounted here a truly inter-national project. It has been enormous fun, as wellas a marvellous experience, to work with him,David Norriss and Oscar Merne over the years,and the great enthusiasm of Paddy O´Sullivanand Chris Wilson at Wexford. We are all deeplyindebted to the late Major Robin Ruttledge whoseenthusiasm for Greenland White-fronted Geesehas run undiminished for many decades. Hiswonderful and stimulating correspondence onthe subject convinced us that this was a goosepopulation worth fighting for, and we thank himfor all the inspiration, information and supporthe gave us.

I have a very special affection for Iceland and therole it plays in the annual cycle of the geese, andI count myself exceptionally lucky to have an ex-cuse to travel there and share their stunning land-scape with the very special inhabitants of thatextraordinary land. My thanks to Óli Einarsson,one very special selfless person, for all he has doneover the years to help us and our invasions. Wethank his family for tolerating our many visitsand in particular thank his parents for the loan oftheir beautiful summerhouse as a base for opera-tions over many years. Johann-Óli Hilmarssonhas provided me with more funny after-dinnerstories and brushes with death than most, andthis larger than life man has come to know White-fronted Geese, through the telescope and the cam-era viewfinder, better than most of us. I thank himfor sharing his considerable talent with usthrough the marvel of camera and film. We havebeen extremely lucky to have the help and sup-port of Arnor Sigfusson and I must thank him andhis very special family who have given me andmy family such warm hospitality in Reykjavíkand such happy memories. Thanks also to all therest of the crew at the Institute of Natural His-tory, who have always been so welcoming to us,especially Ævar Petersen, Oli (“OK”) Nielsen andEinar Þorleifsson. Thanks to also Arnþor Garðars-son at the University of Reykjavík for sharing hisknowledge of Icelandic ornithology, and his in-dulgence of us over many years. In very recent

years, we have made a number of friends at theAgricultural College at Hvanneryi, who have tol-erated our eccentric activities on the farm there.For their kindness, help and hospitality, I wouldespecially like to thank Björn Þorsteinsson andhis wife Anna Guðrún Þórhallsdóttir, as well asSverrir Heiðar Júliússon for his interest and sup-ply of beautiful maps, and Rikharð Brynjólfssonfor his help and knowledge of Phleum. Many havehelped in Iceland over the years, but specialthanks to those who gave up their own time tocome and help with observations of geese, namelyHugh Boyd, David Stroud, Alyn Walsh, IanFrancis, Nicky Penford, Anne Fox, StephanieWarren, Nige Jarrett, Nick Picozzi, John Turner,Roy King, Alastair Duncan, Timme Nyegaard andVinni Madsen.

My years working at Slimbridge were filled withvery happy memories, and it was in this verystimulating environment that I learned so much.I thank the many colleagues who made such animpression on my life at that time, but I must es-pecially thank Carl Mitchell, Janet Kear, Roy Kingand John Turner. It was simply a huge privilege(not to mention enormous fun!) to have workedwith so many talented, dedicated and enthusias-tic people at WWT, in particular, folk such as NigelJarrett and Baz Hughes. I must particularly thankStephanie Warren for her contribution to ourunderstanding of Greenland White-frontedGeese. Mike Bell and Habiba Gitay both providedmathematical support and happy collaborationto this numerical illiterate. Myrfyn Owen waskind enough to permit me to use considerabletime and effort on Greenland Whitefronts, and Iowe him a special thank you for that precious free-dom.

I have been extremely fortunate to work for theDanish National Environmental Research Insti-tute, and to benefit from an invigorating andstimulating working environment there. I mustsingle out the contribution of Jesper Madsen whostands like a beacon in our field and has been sucha source of stimulus and help over many years,his encouragement and inspiration cannot beunderestimated. His kindness and support havebeen a great comfort at all times, not least whenthis work seemed impossible to reconcile withreal life. Thanks to Jesper for also finding the timein his busy life to read and comment upon thisthesis. My thanks also to Stefan Pihl for his friend-ship and kindness, to Henning Ettrup for mak-ing a stupid foreigner feel so accepted in Den-

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mark and to Ebbe Bøgebjerg for the gift of inordi-nate good sense, for his companionship and forjust being larger than life. The Gåsgang, JohnnyKahlert, Preben Clausen and Thomas Bregnballe(latterly with Morten Frederiksen, Barbara Ganter,Mark Desholm and Ole Therkildsen) are the folkwho make the working environment at Kalø sovery unique and all have been gracious enoughto cover me whilst I was drafting this thesis.Thanks to everyone at Kalø for making this sucha stimulating place to be and I feel very privi-leged to have had the chance to work there, espe-cially to Helle Klareskov for her patient produc-tion of this report, but also to Else-Marie Nielsenand Karsten Laursen for their help in its produc-tion. My stay at Kalø has brought me into contactwith so many talented people, and in particular,I must express my thanks to Jens NyelandKristiansen. Jens has been the source of enormousstrength in the last few years, first as a Mastersand latterly as a Ph.D student. His exuberance,enthusiasm and deep insight has awakened agreat deal of the unexpected in me, and I am enor-mously grateful for the many happy hours of(sometimes fruitful!) discussion and collaborativepleasure he has selflessly given. Thanks also toChristian Glahder, who indulged me so by allow-ing us to count geese from aircraft long before Iever dreamt I should move to Denmark. He hasbeen a great colleague and collaborator on anumber of projects, most notably the satellite te-lemetry project that he was so successful in run-ning. Finally thanks to Timme Nyegaard for hisenormous contribution to our understanding ofthe energetics of the Iceland stopover to whichhe has contributed so much.

Finally, Greenland: so many folk have helped usin that spectacular country it is very hard to knowwhere to start. I must say a sincere thanks to Adeleand (the late) Aksel Reenberg and their daughterCamilla who made us all feel part of their veryspecial family in Søndre Strømfjord - Kangerlus-suaq. They have a special place in all our hearts.Knud Vægter, whilst he was based in Kangerlus-suaq, gave us enormous logistical help and withthe help of generous spirit and huge hands, liftedall our hearts. A huge thanks to all the partici-pants in the various expeditions to the breedinggrounds for their company and shared goodtimes: Ian Bainbridge, Dave Beaumont, John Bell,Phil Belman, Johnny Birks, Michael Clausen, Pe-ter Coveney, Jane Claricoates, Phil Davies, (thelate) Nigel Easterbee, Pauline Eddings, DaveElliot, John Floyd, Adie Fowles, Ian Francis, John

Frikke, Barbara Ganter, Mick Green, Inge Guld-berg, Mel Heath, Will Higgs, Nigel Jarrett, AlisonJennings, Lyndsay Kinnes, Jesper Madsen, JimMcCarthy, John McCormack, Clive MacKay, PeteMayhew, Carl Mitchell, Jerry Moore, Jens Nyeland,Mike Peacock, Nicky Penford, Pete Reynolds, SteveRidgill, Judy Stroud, David Stroud, Guy Thomp-son, Alyn Walsh, Stef Warren, Colin Wells andGordon Wright, Many other have helped us thereover the years and I especially would like to thankBill Mattox, Bill Seger, Steen Malmqvist, FinnLarsen, Mads-Peter Heide-Jørgensen, PeterNielsen, Klaus Nygaard, Palle Bo Nielsen, PerPedersen, Leif Pedersen, Henning Thing, NielsThingvad and Niels Gylling Mortensen.

My thanks to many colleagues all over the globewho have happily indulged me at various timesin the vague pursuit of White-fronted Geese.Craig Ely was amongst the first to make us real-ise there were other White-fronted Goose enthu-siasts in the world, as well as supplying us withexperiences and wisdom from other races. Spe-cial thanks to Bob Bromley and Bruno Croft for awonderful time in Walker Bay at 'the place of thePintails' (Kikkaktok) and to Ray Alisauskas andall of his crew for 2 simply wonderful visits toQueen Maud Gulf Migratory Bird Sanctuary. Allof these visits were organised thanks to the gen-erosity and kindness of Hugh Boyd. I also havevery fond memories of working with Bruce Battand Rich Malecki on the embryo Greenland Can-ada Goose project, which resulted in the summeraerial survey of 1999 and satellite telemetry stud-ies on the Canadas. Thanks also to Fred (andSylvia!) Cooke for hosting all the Foxes during abrief study tour on the west coast of Canada tomarshal thoughts. I must also thank Rudi Drentand his remarkable waterbird group for being adistant but important stimulus. Theunis Piersma,in particular, has been an important influence - Iwas deeply saddened to find close to submission(as so often the case) that Figure 9.1 was not anoriginal construction. Piersma & Baker (2000)prove yet again that I do not have an originalthought in my body. Thanks too, to the membersof the Wetlands International Goose SpecialistGroup, who have been such a stimulus and sup-port over the many years since its creation underthe wing of Jesper Madsen. Amongst theirnumber, a special thanks to Bart Ebbinge (the cur-rent co-ordinator), Leif Nilsson, Eckhart Kuijken,Karel Hudec, Dan Munteanu, Johan Mooij, Mi-chael O’Briain, Mike Smart, Geoffrey Matthews,Andrew St. Joseph, Eugeny Syroechovsky and the

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late Lambert van Essen for their particular kind-ness and support over many years.

The counting of geese can be a lonely and soli-tary pursuit, but we have been fortunate in hav-ing legions of folk who happily give of their ownspare time to endure the most horrendous condi-tions, just to count geese or to read the insigniaon a collar. These dedicated people must neverbe forgotten when counts are presented as a sim-ple matter-of-fact graph or annual survival esti-mates are presented without recourse to the manythousands of resighting observations they relyupon. Our work would simply not be possiblewithout the efforts of such folk and it is good for-tune for us to stand on the shoulders of these in-dividuals and use their information, hopefully totheir satisfaction. Although it is unfair to singlepeople out, I would like to thank Malcolm Ogilvie,Óli Einarsson, Jóhan-Oli Hilmarsson, Ross Lilley,Stan Laybourne, Eric and Sue Bignal, KendrewColhoun, Graham McElwaine and Ian Francis inparticular for their special efforts over the years.Thanks to Carl Mitchell and Rich Hearn for send-ing on resightings of Greenland White-frontedGeese. I would also like list those that have madea special contribution either through counts, sur-veys, supply of resightings or have assisted inother ways. They are (with apologies to anyone Ihave forgotten): J. Adair, M. Adam, R.G. Adam, J.Adams, G. Adolfson, D. Allen, G.Q. Anderson, J.Anderson, I.S. Angus, R.A.G. Angus, members ofthe Argyll Bird Club, B. Arnarson, J. Arnold, L.Arnold, S. Aspinall, D. Auld, M. Avery, R. Baine,Dr. I. Bainbridge, M. Ball, T. Banks, H. Barker,W.M. Barr, A.C. Bastable, L.A. Batten, D. Batty, P.Batty, C. Beardall, J. Bell, Prof. D. Bellamy, P.Belman, D. Beaumont, the late P. Behan, M.Bellinger, S. Benn, Dr. E.M. Bignal, M. Bignal, R.Bignal, S. Bignal, M. Bignal, C. Birkenshaw, Dr.J.D.S. Birks, M. Birtwell, R.J. Bleakley, M.Bleasedale, K. Blehein, D. Boardman, BodminMoor Bird Observatory, C.J. Booth, T. Bormann,J. Bowler, H. Boyd, P. Boyer, J. Boyle, members ofvarious Brathay expeditions to count geese onScottish Islands, J. Bratton, S. Breasley, V. Breslin,M. Brierley, R.A. Broad, G.J. Brock, I. Brockway,P. Brooks, G. Brown, D. Browne, D.M. Bryant, I.Bullock, M. Burn, P. Burnham, R.R. Burn, C. & A.Burton, C. Burton, J. Byrne, D. Cabot, Dr C.J. Cad-bury, W.A. Cadman, A. Campbell, the late B.Campbell, C. Campbell, N. Campbell, P. Camp-bell, W. Campbell, J. Carmichael, B. Carrick, J. Car-roll, T. Carruthers, S. Casey, P. Cashman, K.A.H.Cassels, G.P. Catley, R. Calvin, Dr P. Chanin, P.

Charleton, A. Chater and the late Mrs Chater,D.G.P. Chatfield, J. Claricoates, Dr D. Clarke, J. &P. Clarke, S. Clinton Davies, R. Cockerill, J. Cole,M. Cole, D. Coleman, R. Colman, P.N. Collin, A.Colston, W.M Condry, M. Cooke, R. Coomber, J.Corbett, G. Corrigan, C. Corse, P. Cosgrove, D.Cotton, D. Counsell, P.F. Coveney, C. Craik, L.Cranna, C.M. Crawford, G. Cresswell, K. Croft,C. Crooke, C. Crowley, W.A.J. Cunningham, A.Currie, C. Currie, J. Curtis, T. Curtis, P. Dale, T.Dalyell, A. Davidson, P.C.S. & C. Davies, S.C. Da-vies, C. Davis, J. Davis, P.E. Davis, P.J.S. Dawson,T. Dawson, T. Dean, P. Dedicoat, S. Delany, R.H.Denham, R. Dennis, D. Devlin, T.D. Dick, R.C.Dickson, D. Dinsdale, B. & D. Dix, S. Dix, T. Dix,Dr & Mrs R.H. Dobson, P. Dolton, E. Doran, T.Doughty, Dr I.T. Draper, N. Duff, D. Duggan, P.B.Duncan, the late Rev A.R. & Mrs J. Duncan-Jones,T. Durkan, Mr and Mrs J. Dye, A. Easterbee, thelate Dr N. Easterbee, the late J. Eggeling, O.Einarsson, V. Einarsson, N. Elkins, D. Elliot, J.Elliot, M. Elliott, P. Ellis, European Commission,A. Evans, D. & D. Evans, F. Evans, G. Evans, I.Evans, R.J. Evans, K. Fairclough, D. Farrar, M.J.Feehan, A. Fletcher, V. Fletcher, J. Flynn, P. Foley,C. Ford, W.D. Foreshaw, A.P. Fowles, A.E.M. Fox,L. Fox, Dr I.S. Francis, Friends of the Earth,Friends of the Earth (Scotland), J. Frikke, A.Gammell, A. Gardarsson, M. Garnett, J. Gatins,W. Gernander, I. Gibson, D. Gilbert, C. Gladher,P. Goriup, A.G. Gordon, J.J. Gordon, R. Gordon,R. Graham, F. Grant, H. Gray, M. Gray, M. Green,J. Greene, N. & M. Gregory, I. Guldberg, H.Gunnarsson, P. Gyseman, M.J. Hackett, H.Th.Hafsteinsson, K. Hague, P.J. Hall, J. Halliday, F.Hamilton, R. Hamilton, K.J. Hamper, P. Hampson,E.S. Hansen, B. Haran, N. Harding, E. Hardy, Y.Harpin, L. Harrington, S. Hassett, G. Hauksson,R. Hawley, the late C.G. Headlam, S. Heery, J.Heine, J. Hennigan, I. Hepburn, P. Hersteinsson,J. Hesp, S. Hession, M. Heubeck, G. Higgins, J.J.Higgins, W. Higgs, P. Hill, N.E. Hill-Trevor, J.O.Hilmarsson, B. Hjaltason, D. Hogan, J. Holloway,Dr P.G. Hopkins, I. Hopkins, J. How, J. Howe, C.Howie, M.G.B. Hughes, I. Hulbert, D. Hunt, F.Hunter, P. Hurst, C. Huton, staff at ICBP (nowBirdLife International), C. Imboden, members ofthe International Mire Conservation Group, thestaff of the Irish Wildbird Conservancy, D.Jackson, G. Jackson, M. Jackson, D.C. Jardine, N.Jarrett, A. Jenkins, Dr A.R. Jennings, D. Jones, E.Jones, R. Jones, K. Kampp, K. Kane, Z.H.Karpowicz, A. Kerr, A.J. Kerr, Dr T. Keatinge, B.Kilroy, I. Kimber, A. King, L. Kinnes, Dr J. Kirk, J.Kirby, A. Knight, K. Knight, E. Knott, Y. Kolbeins,

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L. Kramer, J.N. Kristiansen, T. Laidlaw, Dr D.R.Langslow, S. Lawrence, E. Laybourne, S. Lay-bourne, D. Lea, A. Leach, F. Leckie, R. Leishman,A.J. Leitch, L. Lenihan, P. Leonard, R. Lilley, R.A.Lindsay, B. Little, Mr & Mrs R. Locken, the lateM. Lohan, B.K. Long, G. Luke, R. Lundy, K.Lydiatt, K. Lynch, L. Lysaght, D. MacAllister, J.MacArthur, E. McCallum, H. McCann, C. McCar-thy, J. McCarthy, J. McCarthy (no relation), I. Mac-Coll, R. Maculloch, L. McDaid, F. MacDonald, I.MacDonald, J. MacDonald, Dr R. MacDonald, M.P.McDonnell, A. McElwaine, G. McElwaine, D.McGill., C. McGuire, C.R. McKay, M. Mackay, M.Mackenzie, R. McKenzie, T. McKerrell, P. Mackie,J. Mackintosh, W. Maclaughlin, D.J. McLaughlin,C. MacLean, L. McLellan, A. Maclennan, I.Macleod, D. McMahon, J. McOwat, J. MacRae, M.Madders, J. Madsen, R. Madsen, J. Magee, C.Maguire, E. Maguire, A. Mainwood, S. Malmquist,E. Manthorpe, D. Massen, R.E. Matson, ProfessorG.V.T. Matthews, J. Matthews, F. Mawby, B.N.K.Mayes, E. Mayes, E. Meek, P. Melchett, O.J. Merne,E.A. Meskil, C.A. Miller, M. Miller, P. Miller, M.Mills, D. Minns, B. Minshull, R. Minter, C.R.Mitchell, J. Mitchell, A. Molloy, S. Money, A. Moore,J. Moore, P. Moore, P. Morgan, E. Morley, Dr G.M.de Mornay, D. Morris, C. Morrison, Dr M. Moser,D. Mower, G.P. Mudge, N. Mulholland, the amaz-ing Iain Munro, C. Murphy, G. Murphy, S. Murphy,J.G. Murray, R. Nairn, NamminersornerullutikOqartussat, B. & J. Neath, M. Needham, B. Neill,B. Nelson, S. Newton, M.J. Nugent, M. O’Briain, P.O’Connell, T. O’Connell, B. O’Connor, P. O’Don-nell, T. O’Donoghue, C. Ogilvie, Dr M.A. Ogilvie,D. O’Higgins, D. Okill, J. O’Keefe, P. O’Leary, D.Orr-Ewing, M. O’Sullivan, P. O’Sullivan, P.J.O’Sullivan, J. Owen, M. Owen, R. Page, J. Palfrey,J. Parslow, D. Patterson, I. Patterson, S. Payne, M.Peacock, N. Penford, H. Pepper, S. Percival, C.Perrins, M. Perrins, Æ. Petersen, L. Petersen, G.Peturssen, M. Phillips, B. Philp, C. Pickup, Dr M.W.Pienkowski, P. Pitkin, R. Pollitt, R. Pollock, L. Pope,R. Porter, B. Prescott, I. Prestt, A. Prins, B. Proctor,R. Quick, B. Rabbitts, A. Rafsson, N. Rankin, J. Ray,P.S. Read, A. Reenberg, A. Reenberg, C. Reenberg,D. Rees, N. Ranwick, P. Reynolds, V. Reynolds, T.

ap Rheinallt, J. Rhead, B. Ribbands, R. Riddington,Big Steve Ridgill, M. Ridgway, N. Roberts, P.Robinson, B. Robson, H. Roderick, C. Rollie, S.Rooke, G. Room, P. Rose, A. Rothwell, F. Rout, M.Rowcliffe, staff of the RSNC, staff of the RSPB,RSPB volunteers at the Loch Gruinart and Ynyshirreserves, N.N. Russell, Major R.F. Ruttledge, J.Ryan, D.G. Salmon, T.S. Sands, C.D. Scotland,members of the Scottish Ornithologists Club, D.Scott, R. Scott, the Joint Nature Conservation Com-mittee Seabirds at Sea Team, C. Secrett, C. Self, G.Sheppard, K.B. Sheppard, R. Sheppard, J. Sher-wood, P. Shimmings, L. Shippy, P. Shorterell, T.Sigurbjörnsson, G. Sigvaldason, D. Silke, P. Sim-mers, A. Sigfússon, D. Silke, K. Skarþedinsson, V.Skat-Rørdam ,J. Skilley, J. Skilling, P. Skinner, M.Smart, P. Smiddy, G. Smith, J. Smith, M. Smith, R.Smith, I. Smitton, A. Snæþorsson, R. Squires, K.Stanfield, D. Stanley, J.G. Steele, A. Stewart, A.Stevenson, M. Stevenson, A.G. Stewart, E. Still, M.Still, L. & S. Street, the late B. Stronach, J. Stoneman,D. Strong, C.J. Stroud, Dr & Mrs R.A. Stroud, J.Stroud, J.M. Stroud, S. Sutton-Jones, R. Swann, E.Sweeney, M. Sweeney, R. Tanner, R. Taylor, R.Thaxton, A.C. Thirlwell, H. Thing, N. Thingvad,V. Thom, D. Thompson, P. Thompson, P.M.Thompson, E.O. Thorleifsson, M. Thornton, D.Thorogood, M. Tickner, R. Tottenham, R. Tozer, M.Trubridge, the late Colin Tubbs, V. Tulloch, C.Tydeman, A. Unnsteinsson, J. Uttley, K. Vaegter,W. Veale, J. van Vessem, P. Vaughan, M. Vikar, S.Votier, P.B. Waldron, E. Wallace, N. Wallace, A.Walsh, P.J. Warner, S.M. Warren, J. Waters, A.D.Watson, Dr J. Watson, J. Watson, T. Weir, C.E. Wells,J. Wells, J. Welstead, the late T. Whilde, C. White,R. White, S. Whyte, staff and volunteers of TheWildfowl & Wetlands Trust, J. Wilkinson, W.Wilkinson, J. Wilkson, T. Williams, C. Wilson, J.Wilson, P. Wormall, M. Wynn, J. Young, B.Zonfrillo. This is not just a long impersonal list -thank you all very much!

Finally, I would like to gratefully acknowledgepermission, granted by the publishers of all thearticles reproduced here, to reproduce thesemanuscripts in this thesis.

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12 Appended manuscripts

1: Fox, A.D. & Madsen, J. (1981) The pre-nesting behaviour of the Greenland White-fronted Goose. Wildfowl32: 48-54.

2: Fox, A.D., Madsen, J. & Stroud, D.A. (1983) A review of the summer ecology of the Greenland White-fronted Goose Anser albifrons flavirostris. Dansk Ornitologisk Forenings Tidsskrift 77: 43-55.

3: Fox, A.D. & Ridgill, S.C. (1985) Spring activity patterns of migrating Greenland White-fronted Geese inWest Greenland. Wildfowl 36: 21-28.

4: Francis, I.S. & Fox, A.D. (1987) Spring migration of Greenland White-fronted Geese through Iceland. Wild-fowl 38: 7-12.

5: Fox, A.D. & Stroud, D.A. (1988) The breeding biology of the Greenland White-fronted Goose Anser albifronsflavirostris. Meddelelser om Grønland, Bioscience. 27: 1-14.

6: Kampp, K., Fox, A.D. & Stroud, D.A. (1988) Mortality and movements of the Greenland White-frontedGoose Anser albifrons flavirostris. Dansk Ornitologisk Forenings Tidsskrift 82: 25-36.

7: Wilson, H.J., Norriss, D.W., Walsh, A., Fox, A.D. & Stroud, D.A. (1991). Winter site fidelity in GreenlandWhite-fronted Geese Anser albifrons flavirostris, implications for conservation and management. Ardea 79:287-294.

8: Warren, S.M., Fox, A.D., Walsh, A. & O’Sullivan, P. (1992) Age of first pairing and breeding among Green-land White-fronted Geese. Condor 94: 791-793.

9: Warren, S.M., Fox, A.D., Walsh, A. Merne, O.J. & Wilson, H.J. (1992) Wintering site interchange amongstGreenland White-fronted Geese Anser albifrons flavirostris captured at Wexford Slobs, Ireland. Bird Study 39:186-194.

10: Bell, M.C., Fox, A.D., Owen, M., Black, J.M. & Walsh, A.J. (1993) Approaches to estimation of survival intwo arctic-nesting goose species. Pp. 141-155 In: Lebreton, J.-D. & North, P.M. (eds.) Marked Individuals inthe Study of Bird Populations. Birkhauser Verlag, Basel.

11: Warren, S.M., Fox, A.d., Walsh, A. & O’Sullivan, P. (1993) Extended parent-offspring relationships in Green-land White-fronted Geese (Anser albifrons flavirostris). Auk 110: 145-148.

12: Fox, A.D., Boyd, H. & Bromley, R.G. (1995) Mutual benefits of associations between breeding and non-breeding White-fronted Geese Anser albifrons. Ibis 137: 151-156.

13: Fox, A.D., Glahder, C., Mitchell, C., Stroud, D.A., Boyd, H. & Frikke, J. (1996) North American CanadaGeese (Branta canadensis) in West Greenland. Auk 113: 231-233.

14: Fox, A.D., Norriss, D.W., Stroud, D.A., Wilson, H.J. & Merne, O.J. (1998) The Greenland White-frontedGoose Anser albifrons flavirostris in Ireland and Britain 1982/83-1994/95: Population change under conser-vation legislation. Wildlife Biology 4: 1-12.

15 Fox, A.D., Kristiansen, J.N., Stroud, D.A. & Boyd, H. (1998) The effects of simulated spring goose grazingon the growth rate and protein content of Phleum pratense leaves. Oecologia 116: 154-159.

16: Kristiansen, J.N., Fox, A.D., Stroud, D.A. & Boyd, H. (1998) Dietary and microtopographical selectivity ofGreenland white-fronted geese feeding on Icelandic hayfields. Ecography 21: 480-483.

17: Fox, A.D., Kahlert, J., Walsh, A.J., Stroud, D.A., Mitchell, C., Kristiansen, J.N. & Hansen, E.B. (1998) Patternsof body mass change during moult in three different goose populations. Wildfowl 49: 45-56.

18: Boyd, H., Fox, A.D., Kristiansen, J.N., Stroud, D.A., Walsh, A.J. & Warren, S.M. (1998) Changes in abdomi-nal profiles of Greenland White-fronted Geese during spring staging in Iceland. Wildfowl 49: 57-71.

19: Fox, A.D., Hilmarsson, J.Ó., Einarsson, Ó, Boyd, H., Kristiansen, J.N., Stroud, D.A. Walsh, A.J., Warren,S.M., Mitchell, C., Francis, I.S. & Nygaard, T. (1999) Phenology and distribution of Greenland White-fronted Geese Anser albifrons flavirostris staging in Iceland. Wildfowl 50: 29-43.

20: Glahder, C.M., Fox, A.D. & Walsh, A.J. (1999) Satellite tracking of Greenland White-fronted Geese. DanskOrnitologisk Forenings Tidsskrift 93: 271-276.

21: Kristiansen, J.N., Walsh, A.J., Fox, A.D., Boyd, H. & Stroud, D.A. (1999) Variation in the belly barrings of theGreenland White-fronted Goose Anser albifrons flavirostris. Wildfowl 50: 21-28.

22: Kristiansen, J.N., Fox, A.D. & Jarrett, N.S. (1999) Resightings and recoveries of Canada Geese Branta canadensisringed in West Greenland. Wildfowl 50: 199-203.

23: Malecki, R.A., Fox, A.D. & Batt, B.D.J. (2000) An aerial survey of nesting Greater White-fronted and CanadaGeese in west Greenland. Wildfowl 51: 49-58.

24: Fox, A.D. & Stroud, D.A. (2002) The Greenland White-fronted Goose Anser albifrons flavirostris. BWP Update4: 65-88.

25: Kristiansen, J.N., Fox, A.D. & Nachmann, G. (2000) Does size matter? Maximising nutrient and biomassintake by shoot selection amongst herbivorous geese. Ardea 88: 119-125.

26: Kristiansen, J.N., Fox, A.D., Boyd, H., Nyegaard T. & Nachmann, G. (submitted). The relationship betweenpreferred food density and grazing white-fronted geese: an example of asymptotic aggregative response.

27: Fox, A.D., Hilmarsson, J.Ó., Einarsson, Ó., Walsh, A.J., Boyd, H. &. Kristiansen, J.N. (in press) Staging sitefidelity of Greenland White-fronted Geese in Iceland. Bird Study 49: 42-49.

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National Environmental Research InstituteThe National Environmental Research Institute, NERI, is a research institute of the Ministry of the Environment.In Danish, NERI is called Danmarks Miljøundersøgelser (DMU).NERI's tasks are primarily to conduct research, collect data, and give advice on problems related to the environ-ment and nature.

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nser albifrons flavirostrisThe annual cycle of a m

igratory herbivore on the European continental fringeNational Environmental Research Institute ISBN 87-7772-719-3Ministry of the Environment