12

Progress Toward Colonial Waterbird PopulationTargets in Hamilton Harbour (1998-2000)

Ralph D. Morris, Cynthia Pekarik, D.V. Chip Weseloh,and James S. Quinn

In the 18th and 19th centuries, thewater body and adjacent land areasknown as Hamilton Harbour werea rich source of biological diversity.Extensive marshlands surroundedall sides of the harbour, with thegreatest density of aquatic vegeta­tion in the shallow west end of thebay, now known as Cootes Paradise.In the early months of the year, thelittoral zone vegetation and wetuplands at the edge of the waterpresumably provided adequatecover for a diversity of breedingland and water birds, and in themonths of September and October,the harbour served as a major stag­ing area for migrating waterfowl.By the mid-1900s, the predictablechanges associated with develop­ment of a major urban and industri­al centre caused the nearshoreareas around much of the harbourto lose the habitat diversity neededto sustain active breeding popula­tions of wildlife species. Marshlandon the south shore of the harbourhad been drained to make way forheavy industry, and the north shorehad been developed as an urbanlandscape with a golf course, yachtclub and extensive housing. Theseand other details on the history and

ONTARIO BIRDS APRIL 2001

more recent status of the harbourwaters and adjacent land areas arefound in the Remedial Action Planfor Hamilton Harbour (1989) andURL site (www.mcmaster.ca/eco­wise/what.htm). Gebauer et al.(1993) offer a historical review ofwaterbird species and populationsin the harbour area.

Throughout the 1990s and intothe new millenium, there are twogeneral land locations around theharbour that remain relatively unde­veloped: the southeast shoreline andCootes Paradise at the extreme westend. Land on the southeast shorehas been owned by the HamiltonHarbour Commissioners (HHC)since the mid-1960s, who manage itfor current and future industrial anddevelopment activities. Portions ofthis land, and five islands in thenortheast corner of the harbour, areoccupied during the breeding sea­son by six species of colonial nest­ing waterbirds (Quinn et al. 1996).The species are: Double-crestedCormorant (Phalacrocorax auri­tus), Black-crowned Night-Heron(Nycticorax nycticorax), HerringGull (Larus argentatus), Ring-billedGull (L. delawarensis) , CaspianTern (Sterna caspia), and Common

Tern (S. hirundo). Curry and Bryant(1987) recorded Snowy Egrets(Egretta thula) nesting in the har­bour in 1986, but they have notbeen recorded there since.

Numbers of nesting pairs, nest­ing locations, and some manage­ment strategies for these species inthe Hamilton Harbour area havebeen reported previously for theyears 1959 through 1987 by Doboset al. (1988), for 1988 through 1994by Moore et al. (1995), and for 1996and 1997 by Pekarik et. al. (1997).Quinn et al. (1996) described threenew wildlife islands whose con­struction was intended to reduceland-use conflict and help maintainavian biodiversity in the harbour.They also proposed long-term man­agement procedures for the water­birds nesting on mainland andisland areas. Our objectives in thisnote are: (1) to record and com­ment on the numbers of nestingpairs in the years 1998, 1999 and2000; (2) to note numerical trendsassociated with each species fromtheir first nesting record to thepresent; and (3) to comment onprogress toward achieving the num­bers of nesting pairs projected inthe Hamilton Harbour RemedialAction Plan (RAP) for the region.

THE STUDY SITEHamilton Harbour (43° 16' N, 79°46' W) is at the extreme western endof Lake Ontario and connects to thelake through the Burlington Canal,

13

a narrow causeway that permitsboat access to the harbour (Figure1). It is separated from LakeOntario by a sandbar, known locallyas the Burlington Beach Strip.

The primary areas of undisturbedbreeding habitat for all six species ofcolonial nesting birds are at the east­ern end and southeastern shorelinesof the harbour (Figure 1). The twomost northerly nesting sites at theeast end of the harbour (Farr andNeare Islands) are simple rock pilesconstructed to support hydro towersand cables (since removed) thatcrossed the harbour (Morris et al.1976). Three new islands (North,Centre, and South Islands in Figure1) built during the winter of 1995-96(Quinn et al. 1996), to provide newnesting habitat in the harbour, areimmediately to the southeast ofFarr and Neare Islands. The largestnesting area for colonial waterbirdsis adjacent to the QEW highway onproperty currently owned and man­aged by the HHC. In the threeyears of our study, all six species ofcolonial birds that breed in the har­bour area nested at various loca­tions on the island and mainlandsites, including the dikes and areasurrounding the confined disposalfacilities locally known as Piers 25,26 and 27 (Figure 1). Three of thesespecies also were recorded at otherlocations within the harbour basin.Ring-billed Gulls nested on the eastside of Windermere Basin to thesouth of Pier 25, and Common Ternsoccupied Spur Dyke Island in

VOLUME 19 NUMBER 1

14

Neare Island D

"\Canada Centre

for Inland Waters

HamiltonHarbour

Stelco

o,scale

LakeOntario

1 kmI

Figure 1: The study areas at the eastern end of Hamilton Harbour, Lake Ontario.The inset locates Hamilton Harbour at the extreme western end of LakeOntario.

ONTARIO BIRDS APRIL 2001

Windermere Basin and somesmall shoals offshore fromLaSalle Park at the west end ofHamilton Harbour. Double-crest­ed Cormorants nested at theextreme northwest end of the har­bour at Carroll's Point, and onHickory Island in CootesParadise, a marshland west ofHamilton Harbour and connectedto it by a short abandoned chan­nel (Desjardins Canal).

METHODSGeneral Principles of a Nest CensusFor most colonial waterbird speciesthat nest in Hamilton Harbour andelsewhere, patterns of clutch starts(laying of the first egg in a clutch) ina particular breeding season arecharacterized by a nesting "peak"that starts within 7-10 days after thefirst clutch appears, and continuesfor the next 7-10 days, with smallnumbers of clutches started there­after. The optimal census protocol ina particular breeding season is toconduct a count of the number ofnesting pairs during the final weekof incubation for clutches initiatedbefore and during the peak periodof nest starts. A census conducted atthis time (about 10 days after the last"peak" clutch is initiated) alsocounts clutches started in the 10 daysfollowing the peak of egg laying.Thus, the census counts 90-95 % ofall clutches started in a particularyear, and takes place during a timewhen the majority of young chickspresent are not yet mobile, and so

15

minimizes the risk of disturbance tothe colony (see Brown and Morris1995).

Specific Nest Census Methods(1998-2000)The census methods to estimatenumbers of nesting pairs at the var­ious locations within our study sitegenerally replicated thosedescribed in detail by Pekarik et al.(1997), and used in previous years.Hickory Island, Carroll's Point andother locations around theHamilton Harbour shoreline weresurveyed for Double-crestedCormorant and Black-crownedNight-Heron nests from a boat orfrom the shore. Dates of these sur­veys were mid- to late May. Themainland nesting locations atEastport (Piers 25, 26 and 27), thelands adjacent to WindermereBasin, and all six islands within thestudy area were surveyed fromearly May to mid-June in each year.In general, Ring-billed and HerringGulls were censused from early tomid-May, whereas Common andCaspian Terns were censused fromlate May to mid-June. With theexception of Ring-billed Gulls, thecensus of all species was accom­plished by counting "active nests"(nest scrapes, clutches, broods)within each relatively small nestingarea. For the large nesting areas ofRing-billed Gulls, a team of fieldworkers laid successive parallellines approximately four metresapart across the length of each sur-

VOLUME 19 NUMBER 1

16

vey area. Individual members of theteam walked along each line, count­ing "active nests" within the areabetween the two lines.

Management MethodsFour specific management methodswere used in each year to encour­age (or discourage) the nesting ofindividual species pairs at designat­ed locations throughout the studyarea. First, in late March or earlyApril each year, plastic sheetingwas laid over the substrate of anelevated mound at the north end ofNorth Island that was designatedfor Caspian Tern nests (Quinn et al.1996). Ring-billed Gulls arrive ear­lier in a breeding season and beginnesting before Caspian Terns (ct.Morris et al. 1992 for CommonTerns), and the purpose of the plas­tic was to restrict gulls from nestingon the mound. Second, a commer­cial falconry company was hired ineach year to use raptors to restrictthe nesting of Ring-billed Gulls onthe new wildlife islands and por­tions of Piers 26 and 27. Raptors[primarily Saker Falcons (Falcoscherrug) , Harris's Hawks(Parabuteo unicinctus), andFerruginous Hawk (Buteo regalis)]were in place from late Marchthrough late May. Third, Ring-billedGull nests were destroyed and eggscollected under a federal permit inareas where the two previous tech­niques were unsuccessful at restrict­ing nesting. Fourth, dead standingvegetation from the previous sea-

ONTARIO BIRDS APRIL 2001

son was left in place on Spur Dykein Windermere Basin, as the vegeta­tion discouraged gulls from nestingthere. In 1998, we removed the veg­etation in late April, prior to occu­pancy by Ring-billed Gulls. In 1999and 2000, Ring-billed Gulls colo­nized the Dyke despite the pres­ence of dead standing vegetation,and we periodically collected theireggs from the site (under permit).

RESULTSNumbers of Nesting PairsThe numbers and locations of nest­ing pairs of Ring-billed Gulls,Herring Gulls and Double-crestedCormorants in the HamiltonHarbour area for the three years ofour study are given in Table 1. Sixsites contained Ring-billed Gullnests in 1998 and 1999, with twoadditional sites (shoals betweenislands) colonized in 2000. Thegreatest numbers of Ring-billedGull nests in both years were atWindermere and Eastport, the twotraditional nesting locations forgulls in the Hamilton Harbourbasin over the past decade. Smallernumbers of nests were found on thethree new wildlife islands, with thegreatest number on Centre Islandin each year. Herring Gulls nestedon 7-8 sites, although only five siteshad nests in all three years (Table1). The greatest numbers of HerringGull nests in each year were onNeare Island, with fewer nest num­bers on the adjacent Farr Island tothe north (Table 1). Of the three

17

Table 1: Numbers of nesting pairs of Ring-billed Gulls (RBGU), Herring Gulls(HEGU) and Double-crested Cormorants (DCCO) nesting in theHamilton Harbour area in 1998-2000. Total numbers of all six species aresummarized in Table 3.

Location RBGU HEGU DeeO1998 1999 2000 1998 1999 2000 1998 1999 2000

Hickory lsI. 0 0 0 0 0 0 218 222 197Carroll's Point 0 0 0 0 0 0 13 0 0Windermere l 9,337 10,080 7,8292 4 0 0 0 0 0Spur Dyke 12 106 200 3 0 0 0 0 0Eastport 5,902 11,072 14,616 16 39 43 588 820 873Raft3 0 0 0 0 1 1 0 0 0Neare lsI. 0 0 0 114 109 111 0 0 0Farr lsI. 0 0 0 34 43 43 23 40 48North lsI. 49 137 135 62 74 66 0 0 0Centre lsI. 1,275 2,0004 745 14 0 3 255 255 255

South lsI. 0 195 159 0 0 0 0 0 0Shoals (C-S)6 0 0 51 0 1 0 0 0 0Shoals (C-N)7 0 0 24 0 0 1 0 0 0Breakwall8 0 0 0 NC 7 3 0 0 0

1 east side of Windermere Basin

2 east and west sides of Windermere Basin

3 artificial wooden raft anchored in pond south of Pier 274 estimate based on nests in 2-3 1 X 1 m quadrats, extrapolated to dimensions of the island5 nests on five ledges attached to each of five telephone poles (25 ledges each year)

6two shoals between Centre and South islands; 36 nests on north shoal and 15 nests on southshoal

7 two shoals between Centre and North islands; all 24 nests on south shoal8 west of Canada Centre for Inland Waters9 NC = not censused

new wildlife islands (North, Centre,and South), North Island containedthe largest numbers of nestingpairs. Nests at the Eastport sitewere concentrated along Pier 27 atthe north edge of the confined dis­posal facility. Double-crestedCormorants nested at the same fourlocations in each year (Table 1), andat Carroll's Point. The Eastport sitecontained the greatest number ofnesting pairs.

The numbers and locations ofnesting pairs of Common Terns,Caspian Terns and Black-crownedNight-Herons for the three years ofour study are given in Table 2.Common Terns nested at sevenlocations in 1998, although thegreatest numbers of nests were ontwo islands, Spur Dyke and CentreIsland. In 1999, Spur Dyke againcontained the greatest number ofnesting terns, although the number

VOLUME 19 NUMBER 1

18

was estimated upwards from anactual count of 242 clutches on 14May, shortly after peak nesting.Nest numbers on Centre Islanddropped to zero in 1999, balancedby an increase in numbers of nest­ing pairs on South Island. The mostsignificant change in 2000 was adecrease in the number of nests onSpur Dyke (Table 2). The LaSallePark Shoals contained small num­bers of pairs in all years. Nesting ofCaspian Terns was restricted to thesame two locations in each year,with the North Island site favouredover the Centre Island location(Table 2). Black-crowned Night-

Herons nested at four locations in1998, and two locations in 1999 and2000, with consistent numbers ofnests on North Island in all years.The Eastport site had the largestnumber of nesting pairs in 1999 and2000.

A direct comparison of numbersof nesting pairs over the three yearsfor all six species is in Table 3. Ring­billed Gulls were clearly the numer­ically dominant species, followed byDouble-crested Cormorants,Common Terns, Caspian Terns,Herring Gulls, and Black-crownedNight-Herons. While the actualnumbers of nests for the different

Table 2: Numbers of nesting pairs of Common Terns (COTE), Caspian Terns(CATE) and Black-crowned Night-Herons (BCNH) nesting in theHamilton Harbour area in 1998-2000. Total numbers of all six species aresummarized in Table 3.

Location COTE CATE BCNH1998 1999 2000 1998 1999 2000 1998 1999 2000

LaSPSh 11 8 7 8 0 0 0 0 0 0LaSPSh 2 19 5 17 0 0 0 0 0 0Spur Dyke2 339 3633 292 0 0 0 0 0 0Eastport 0 0 0 0 0 0 7 68 96Neare lsI. 0 0 0 0 0 0 4 0 0North lsI. 0 0 0 303 280 309 31 36 374

Centre lsI. 166 0 0 130 141 106 10 0 0South lsI. 75 2475 232 0 0 0 0 0 0Shoal (C-S)6 1 0 0 0 0 0 0 0 0

1 LaSalle Park Shoals (N = 5)

2 Spur Dyke in Windermere Basin (Figure 1)

3 estimated from mainland on 18 June (242 clutches counted 14 May)

4 abandoned or washed away by high water sometime after 24 May 2000

5 nests with immobile chicks counted on 14 June; additional nest numbers estimated fromchick groups

6north shoal between Centre and South islands

ONTARIO BIRDS APRIL 2001

19

Table 3: Estimated total numbers of nesting pairs of six colonial waterbird speciesin the Hamilton Harbour area in 1998-2000. The percentage change is from1998 to 2000.

Species 1998 1999 2000 Percent change(1998-2000)

Black-crowned Night-Heron 52 105 133 +155.8Ring-billed Gull 16,575 23,590 23,884 +44.1Double-crested Cormorant 867 1,107 1,143 +31.8Herring Gull 247 273 271 +9.3Caspian Tern 433 421 415 -4.2Common Tern 620 626 562 -9.4Total 18,789 26,016 26,408 +40.5

species varied over several orders ofmagnitude, the greatest percentageincrease was experienced by Black­crowned Night-Herons (Table 3).Four of the six species realized a per­centage increase in numbers of nest­ing pairs; both tern speciesdecreased over the three years, withCommon Terns losing almost 100/0of their nest numbers between 1998

and 2000. The total number of nest­ing pairs increased by 40.5%.

Specific Nesting SitesThe numerical data provide noinformation on specific sites withinthe nesting locations that containedthe greatest number of nests.Accordingly, we briefly comment onthese details for each major location.

EastportEastport contained nests of Ring-billed Gulls, Herring Gulls, Double-crested Cormorants, andBlack-crowned Night-Herons (Tables 1 and 2). The nests of cormorants and herons were con­centrated in a small grove of willow (Salix sp.) and Manitoba (Ashleaf) Maple (Acer negundo)bushes, and dead Eastern Cottonwood (Populus deltoides) trees along the west edge of the con­fined disposal facility (CDF) between Piers 26 and 27 (see Figure 1). Heron nests were restrict­ed to the willow bushes; cormorant nests were in the maple and cottonwoods. The cottonwoodssupported substantial numbers of cormorant nests in earlier years, but by 1998 were largely col­lapsed and the birds were mostly nesting on the remaining low branches of broken tree stumpsor on the ground. Ring-billed Gulls nested on all land areas around the CDFs, while the small­er numbers of Herring Gull pairs nested primarily along the dike on the edge of the mostnortherly CDF (Figure 1). The Hamilton Harbour Commissioners contracted with falconrycompanies in each of the three years to position raptors at strategic locations along the south­ern edge of Pier 26 to control the nesting of Ring-billed Gulls. Gulls were permitted to nest onland areas north of a point about 20 m south of the southerly CDF.

Windermere and Spur DykeThe land areas around Windermere Basin and Spur Dyke on the west side of the Basin con­tained nests of Ring-billed Gulls, Herring Gulls and Common Terns. The highest density ofRing-billed Gull pairs was on the east side of Windermere Basin in a narrow strip of approxi­mately 30 m along the shoreline, extending northward to the bridge across the Windermere

VOLUME 19 NUMBER 1

20

Channel (Figure 1). Ring-bills also nested along the northern edge of Windermere Basin. Thefew Herring Gull nests were on the east shore of the Basin and on Spur Dyke. Common Ternsnested exclusively on the eastern half of Spur Dyke in all three years.

Neare and Farr IslandsEach island contained nests of two species: Herring Gulls and Black-crowned Night-Herons onNeare Island, and Herring Gulls and Double-crested Cormorants on Farr Island. Nests wereevenly distributed around each island. Cormorants nested on the ground and in a singleManitoba Maple on Farr Island.

Wildlife Islands (North, Centre, and South)While the substrates on each of the three islands were constructed to encourage colonizationby particular species of colonial waterbird (details in Quinn et al. 1996, Pekarik et al. 1997), set­tlement in the three years of our study was not always as planned. Heavy vegetation coveredSouth Island, and only Ring-billed Gulls and Common Terns nested there, with tern nests con­centrated around the northern (1998 and 1999) and southern (2000) edges. Gull nesting onSouth Island was successfully prevented with the use of a raptor in 1998, but pairs again colo­nized the island in 1999 and 2000 (Table 1) despite the presence of a raptor there. Centre Islandsupported nests of all six species in 1998, three species in 1999, and four species in 2000 (Tables1 and 2). Double-crested Cormorants nested exclusively on the ledges on poles in the middleof the island; none nested on the ground. Caspian Terns nested on an elevated mound at thenorth end of Centre Island, while Ring-billed Gulls nested throughout. On North Island,Caspian Terns nested on mounds at both the north and south ends of the island, while Black­crowned Night-Herons nested in the rocks around the edges of the island. Herring and Ring­billed Gull nests were distributed throughout.

Hickory Island/Carroll's PointDouble-crested Cormorant nests were exclusively in trees on Hickory Island and at Carroll'sPoint.

Historical dataNumbers of nesting pairs using theHamilton Harbour area in 1998 and1999 can be better placed into per­spective by comparing them withnumbers recorded in earlier years(Table 4). Common Terns were thefirst recorded nesters in HamiltonHarbour (1946), while CaspianTerns were the most recent arrivals(1986). In the 12 years after system­atic counting began in 1987, num­bers of Common Tern and HerringGull pairs remained relatively con­stant. Numbers of Caspian Ternpairs have experienced a three-foldONTARIO BIRDS APRIL 2001

increase, whereas numbers ofDouble-crested Cormorants haveincreased by a factor of 20.Conversely, numbers of nestingBlack-crowned Night-Heron pairsdeclined through the mid-1990s, butexperienced a resurgence in 1999that brought numbers to about halfthose present in 1987. Numbers ofRing-billed Gull pairs appear sta­ble. However, there was only onesystematic count of Ring-billedGull nests in Hamilton Harbourbetween 1987 and 1999, and num­bers of nesting pairs in that year(1990; Blokpoel and Tessier 1996)

21

Table 4: Estimated numbers of nesting pairs of waterbirds in the Hamilton Harbourarea from the year when nesting was first recorded through successivemajor count dates. The target numbers were established by an ad hoc com­mittee of research and policy personnel with the objective of reaching themby 2003 (see text).

Species Number of nestin2 pairsFirst count 1,5 19872 19943 19974 2000 Tar2et

Black-crowned Night-Heron 15 (1959) 212 90 20 133 200Ring-billed Gull 2 (1961) 21,207 Ne NC 23,884 5,000Double-crested Cormorant 1 (1984) 51 451 495 1,143 200Herring Gull 7 (1976) 225 303 342 271 350Caspian Tern 48 (1986) 134 313 399 415 >200Common Tern 15 (1946) 553 868 753 562 >600

1year of first count in parentheses

2 numbers from Dobos et al. 1988

3 numbers from Moore et al. 1995

4 numbers from Pekarik et al. 1997

sfrom citations in Dobos et al. 1988

6 no count; 39,621 pairs counted by Blokpoel and Tessier (1996) in 1990 (see text)

were almost double (39,621) thatreported in 1987 and 1999. Themost probable reason for thedecline in the 1990s is related tomanagement activities contractedby the Hamilton HarbourCommissioners (see below).

DISCUSSIONIn recent historical times (since themid-1970s), the land areas designatedas Piers 25 through 27, and that sur­rounding Windermere Basin, havebeen owned by the HamiltonHarbour Commissioners who haveused it for their own purposes (1.Brookfield, pers. comm.). Becauseaccess to these properties is restrictedby the HHC, the sites provide rela­tively secure nesting habitat for colo­nial nesting waterbirds. Details ongeneral nesting location and numbers

of breeding pairs for the six waterbirdspecies nesting in the HamiltonHarbour area have been reported forthe years 1959 through 1997 (Doboset al. 1988, Moore et al. 1995, Pekariket al. 1997), and Dobos et al. (1988)provided details of historical nestingdata for some of the species.

Numerical patterns over theyears since the first count (Table 4)can be taken as representative oflocal population changes for five ofthe six species in the HamiltonHarbour area; the pattern for Ring­billed Gulls cannot. The dramaticincrease in the numbers of breedingpairs in the 26 years between 1961and 1987 (+ 21, 205) probably is anaccurate indication of the exponen­tial numerical increase of which thisspecies is capable. Ring-billed Gullsare tolerant to disturbance in their

VOLUME 19 NUMBER 1

22

breeding colonies (Brown andMorris 1994), are adaptive omni­vores compared to Herring Gulls(Chudzik et al. 1994), and haveexperienced eruptive growth innumbers at colonies in the lowerGreat Lakes between 1976 and1990 (Blokpoel and Tessier 1996).Conversely, while the relativelysmall increase in numbers of breed­ing pairs in the 12 years between1987 and 2000 (+ 2,677) might sug­gest habitat saturation, the morelikely explanation is the manage­ment activities of the HHC thatoperate to control the nesting loca­tions of gulls. Management tech­niques have included pyrotechnics,physical disturbance, egg collection,and the use of falconry. Withoutthese controls that started in theearly 1990s, the colony is likely tohave increased at the average annu­al growth rate of 11.6 - 12.60/0reported for colonies elsewhere inLakes Erie and Ontario (Blokpoeland Tessier 1996). Some evidencefor this suggestion comes from theonly systematic count of Ring­billed Gull nests in HamiltonHarbour between 1987 and 1999;numbers in that year (1990) werealmost double (39,621) that report­ed in 1987 (21,207). Accordingly,the decrease in nesting pairs fromthe 1990 numbers to 23,884 pairs in2000, is apparently the result of theuse of falconry and other proce­dures to restrict nesting to areasdesignated by the HamiltonHarbour Commissioners.

ONTARIO BIRDS APRIL 2001

Raptors were the principalmeans used to control nesting byRing-billed Gulls during the threeyears of our study. Although thecontrol objectives were the same ineach year (to restrict Ring-billedGull clutches from major sectionsof Eastport, from most of the landon the east shore of WindermereBasin, and from the three newwildlife islands), there was a signifi­cant increase in the total number ofclutches recorded at all locations in1999 (23,590) compared to 1998(16,575). Conversely, in 2000, num­bers remained relatively stable(23,884). The increase in 1999 fol­lowed by relative stability in 2000,may reflect differential efficiency inthe use of raptors to control nestinggulls. Two different falconry compa­nies were employed by the HHCand the Canadian Wildlife Servicein 1998 [Bird Control InternationalInc. (BCI)] and 1999 [FalconInternational (FI)]. BCI was againemployed in 2000 to control gullnesting and there was no increasefrom the number of nests in 1999.Furthermore, the use of a large rap­tor on Centre Island in 2000 signifi­cantly reduced numbers of Ring­billed Gulls nesting there comparedto the previous year (Table 1).Whether the required five-foldreduction to the target numbers ofnesting Ring-billed Gulls is possiblewill depend on the continued andefficient use of raptors at Eastport,Windermere Basin and the newwildlife islands.

Targeted Numbers of Nesting PairsThe Remedial Action Plan forHamilton Harbour (1989) identifieda need to create permanent habitatfor colonial nesting birds within theharbour area (J. Hall, pers. comm.),and Quinn et al. (1996) argued forthe importance of maintaining avianbiodiversity there. As an integralpart of the creation of new habitat onthe three new wildlife islands, andthe management of waterbirdspecies using existing and new nest­ing substrate, an informal ColonialWaterbird Nesting Committee wasstruck to establish desirable targetsfor each species nesting in the har­bour area. The Committee, com­posed of personnel from the Fish andWildlife Habitat Restoration Project,the Canadian Wildlife Service,McMaster University and BrockUniversity, established target num­bers of nesting pairs for each specieswith the objective of meeting thenumbers with appropriate manage­ment procedures by the year 2003.

Targets for Common Terns andCaspian Terns were approached orexceeded in 2000 (Table 4).Management efforts used to date(cf. Morris et al. 1992, Quinn et al.1996) indicate that both ternspecies can likely be sustained attheir current nesting locations onthe new wildlife islands and SpurDyke. However, both speciesrequire the implementation of spe­cial management procedures eachyear. Ring-billed Gulls are prevent­ed from nesting on Common Tern

23

and Caspian Tern substrate by acombination of egg removal andraptor use. In addition, sections ofthe Caspian Tern substrate on thenew wildlife islands are coveredeach spring by PVC sheeting untilterns arrive. Despite these efforts,the gradual decline in numbers ofCaspian Terns over the past threeyears, and the 100/0 reduction innumbers of Common Terns since1998, indicate the importance ofcontinued vigilance.

Black-crowned Night-Heronswere at the target number in 1987and will likely reach the numberagain in the next 3-4 years, giventhe substantial increase in pairsfrom 1997 to 2000 (Table 4).Hawthorn (Crataegus sp.) busheson South Island were plantedspecifically to encourage herons tonest there, and we anticipate thatpairs now nesting on the ground onNorth Island will settle into themore suited arboreal habitat astrees mature in the next few years.While the number of Herring Gullpairs declined in 2000, the speciesclearly has potential to reach levelsthat were already at the target num­ber in 1997 (Table 4). We anticipatelittle difficulty in maintaining targetnumbers for these two species.

Current numbers of nesting pairsof Double-crested Cormorants andRing-billed Gulls are each about fivetimes higher than target levels (Table4), and will be difficult to reduce by2003 without the use of major andintrusive management procedures.

VOLUME 19 NUMBER 1

24

Greater use of raptors and moreintensive egg collections are almostcertainly required in future years toreduce numbers of Ring-billed Gulls.We note that the target number forRing-billed Gulls may be subject torevision (in either direction) based onthe outcome of discussions currentlyunderway between the City ofHamilton and the HHC concerningthe ownership of the land east ofWindermere Basin.

In our view, the most seriousproblem is with Double-crestedCormorants that were already wellover the target number of pairs in1994, and that have increased dra­matically in the three years since1997 (Table 4). The nesting poles onCentre Island supported the maxi­mum number of nesting pairs ineach of the past two years, andHickory Island may also be at carry­ing capacity (Table 1). Numbers oftree-nesting pairs at these two loca­tions can likely be maintained

Literature CitedBlokpoel, H. and G.D. Tessier. 1996. Atlas of

colonial waterbirds nesting on theCanadian Great Lakes, 1989-1991. Part 3.Cormorants, gulls and island-nesting ternson the lower Great Lakes system in 1990.Canadian Wildlife Service TechnicalReport series No. 225, Ontario Region.

Brown, K.M. and R.D. Morris. 1994. The influ­ence of investigator disturbance on thebreeding success of Ring-billed Gulls(Lams delawarensis). Colonial Waterbirds17:7-17.

Brown, K.M. and R.D. Morris. 1995.Investigator disturbance, chick move­ment, and aggressive behavior in Ring­billed Gulls. Wilson Bulletin 107: 140-152.

ONTARIO BIRDS APRIL 2001

because of limited branch nestingsites. The greatest concentration ofnesting pairs in Hamilton Harbouris at Eastport in the northwest cor­ner of Pier 27 (Figure 1). Many ofthe birds there construct nests onthe ground, and as space is not yetlimiting, there is a potential for con­tinuing increase. Accordingly, unlessthe target number for this species isrevised upward, intrusive manage­ment procedures will be needed todiscourage nesting at this site.

AcknowledgementsWe thank John Hall, Jeff Brookfieldand Donna Stewart for comments onthe manuscript. We also thank theHamilton Harbour Commissioners,in particular Jeff Brookfield and BillFitzgerald, for cooperation in givingus access to their mainland proper­ties and to Spur Dyke, and for pro­viding partial funding for use of rap­tors to control nesting locations ofRing-billed Gulls.

Chudzik, J.M., K.D. Graham, and R.D.Morris. 1994. Comparative breeding suc­cess and diet of Ring-billed Gulls andHerring Gulls on South Limestone Island,Georgian Bay. Colonial Waterbirds 17:18-27.

Curry, R. and G.D. Bryant. 1987. SnowyEgret: a new breeding species for Ontarioand Canada. Ontario Birds 5: 64-67.

Dobos, R.Z., J. Struger, H. Blokpoel, andD.V. Chip Weseloh. 1988. The status ofcolonial waterbirds nesting at HamiltonHarbour, Lake Ontario, 1959-1987.Ontario Birds 6: 51-60.

Pekarik, c., A.N. Nicassio, H. Blokpoel, D.V.Weseloh, J. Hall, S. Fink, C. Anderson,and J.S. Quinn. 1997. Management ofcolonial waterbirds nesting in HamiltonHarbour: the first two years of coloniza­tion of artificial islands and populationtrends. Canadian Wildlife ServiceTechnical Report series No. 287, OntarioRegion.

Quinn, J.S., R.D. Morris, H. Blokpoel, D.V.Weseloh, and P.J. Ewins. 1996. Design andmanagement of bird nesting habitat: tac­tics for conserving colonial waterbird bio­diversity on artificial islands in HamiltonHarbour, Ontario. Canadian Journal ofFisheries and Aquatic Sciences 53(Supplement 1): 45-57.

Remedial Action Plan for HamiltonHarbour. 1989. Stage I report: environ­mental conditions and problem definition.Environment Canada, Burlington,Ontario.

25

Gebauer, M.B., R.Z. Dobos and D.V.Weseloh. 1993. Historical review of waterand bird populations and annotated list ofwater birds associated with BurlingtonBay, Lake Ontario, 1857-1990. OccasionalPaper No. 78, Canadian Wildlife Service,Ottawa.

Moore, D.J., H. Blokpoel, K.P. Lampman,and D.V. Weseloh. 1995. Status, ecologyand management of colonial waterbirdsnesting in Hamilton Harbour, LakeOntario, 1988-1994. Canadian WildlifeService Technical Report series No. 213,Ontario Region.

Morris, R.D., H. Blokpoel, and G.D. Tessier.1992. Management efforts for the conser­vation of Common Tern colonies: two casehistories. Biological Conservation 60:7-14.

Morris, R.D., R.A. Hunter, and J.F.McElman. 1976. Factors affecting thereproductive success of Common Tern(Sterna hirundo) colonies on the lowerGreat Lakes during the summer of 1972.Canadian Journal of Zoology 54:1850-1862.

Ralph D. Morris, 275 Foss Road, R.R. 5, Fenwick, Ontario LOS 1CO

Cynthia Pekarik, Canadian Wildlife Service, 4905 Dufferin Street,Downsview, Ontario M3H 5T4

D.V. Chip Weseloh, Canadian Wildlife Service, 4905 Dufferin Street,Downsview, Ontario M3H 5T4

James S. Quinn, Department of Biology, McMaster University, Hamilton,Ontario L8S 4Kl

RIVER INN B&BLocated in the Fisherville-Cayuga area (the Raptor capital of Ontario)

Situated in a 14 acre park-like setting on the Grand River• close to Provincial Parks & Lake Erie

• 3 rooms to choose from, ensuite baths, full breakfast, TV, CA• Guests share sitting room, decks, sunporch, pool

• Open all year, Rates $55-75 Canadian - Visawww.Linetap.com/riverinn Email: riverinn@linetap.com 905-774-8057

CaLL ToLL Free 1-866-824-7878759 Regional Rd. 17, RR#l, Cayuga, ON Canada NOA lEO

Your hosts Frank & Helen Belbeck

VOLUME 19 NUMBER 1