SOTEAG ORNITHOLOGICAL MONITORING PROGRAMME€¦ · 2015. Statistics: number of counts, range, mean,...

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SOTEAG ORNITHOLOGICAL MONITORING PROGRAMME

2015 REPORT

Martin Heubeck and Mick Mellor,

Aberdeen Institute of Coastal Science and Management,

University of Aberdeen.

February 2016

CONTENTS

Page 2015 Executive Summary 2

1. Monitoring of cliff-breeding seabirds

1.1. Weather 3 1.2a. Northern Fulmar Fulmarus glacialis: Population counts 4

1.2b. Northern Fulmar Fulmarus glacialis: Breeding success 5

1.3a. European Shag Phalacrocorax aristotelis: Population counts 8 1.3b. European Shag Phalacrocorax aristotelis: Breeding success 10

1.4a. Black-legged Kittiwake Rissa tridactyla: Population counts 12

1.4b. Black-legged Kittiwake Rissa tridactyla: Breeding success 13 1.5a. Common Guillemot Uria aalge: Population counts 16

1.5b. Common Guillemot Uria aalge: Breeding success and chick diet at Sumburgh Head 18

1.5c. Common Guillemot Uria aalge: Breeding success at Burravoe, Yell 23

1.6a. Razorbill Alca torda: Population counts 24 1.6b. Razorbill Alca torda: Breeding success at Sumburgh Head 25

2. Pre-breeding counts of Black Guillemots Cepphus grylle 26

3. Breeding Red-throated Divers Gavia stellata in Northmavine 29

4. Shetland-wide census of moulting Common Eiders Somateria mollissima 30

5. Winter counts of seaduck and diving seabirds 33

5.1. Yell Sound and Sullom Voe 33 5.2. Rova Head to Kirkabister, East Mainland 35

5.3. Whiteness Voe to Skelda Voe, West Mainland 36

6. Beached Bird Surveys

6.1. Incidence of oiling 37

6.2. Non-oiled mortality 39

7. Publications 41

8. Acknowledgements 41

Appendix 1. Seabird monitoring on Foula in 2015 42

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2015 Executive Summary


Northern Fulmar Fulmarus glacialis. A 7% decrease in apparently occupied sites may have been partly due

to heavy rain in May, with some nest sites waterlogged; breeding success was 27% lower than in 2014.

European Shag Phalacrocorax aristotelis. Nest counts in SE Mainland (456) were similar to 2014 (422) but

48% lower than in 2010 (877). Laying was earlier than in 2013-14, and breeding success was high at Sumburgh

Head (1.41 fledged per laying pair) but only moderate at Burravoe, Yell (0.80).

Black-legged Kittiwake Rissa tridactyla. Colony counts were made at No Ness, Troswick Ness and Boddam,

where there were 18% fewer nests (179) than in 2014 (217). Breeding success at six colonies averaged 0.10 ± 0.03 SE chicks fledged per laying, with most losses in late June and early July at the hatching and early chick

stage, suggesting a problem with food supply then.

Common Guillemot Uria aalge. There was little change since 2014 in numbers in population monitoring plots, with the population index at c.45% of the level of 1978, when counts for SOTEAG began. At Sumburgh

Head, breeding success (0.52 fledged per laying pair) was similar to the 1989-2014 mean (0.54); chick diet

was a mix of gadids (55%, mostly presumed Norway Pout) and sandeels (42%). At Burravoe, heavy rain in late May caused egg losses but chick survival was high and success was 0.51 per laying pair.

Razorbill Alca torda. At Sumburgh Head, there was little change since 2014 in population monitoring plots, and numbers remain 70% lower than in 1978; breeding success at 67 sites was 0.57 fledged per laying pair.

2. Pre-breeding counts of Black Guillemots Cepphus grylle

Numbers of adults at monitored coasts surveyed in good conditions were within +16% and -14% of most recent counts in 2013/14. The total of 1,636 adults counted in 2015 was 15% lower than in 2012 (1,929), the

last spring there was full coverage of all ten sections of monitored coasts.

3. Breeding Red-throated Divers Gavia stellata in Northmavine The biennial survey of the moorland between Sullom Voe and St Magnus Bay located 22 confirmed breeding

attempts (26 in 2013) plus empty nest scrapes at 8 other lochs (4). Ten chicks were assumed to have fledged, giving rather low breeding success of 0.45/confirmed breeding attempt (0.38 in 2013).

4. Shetland-wide census of moulting Common Eiders Somateria mollissima The triennial August census located 4,610 birds (of all ages) compared to 4,627 in 2012; 82% of the total was associated with aquaculture sites (64% in 2012). The largest concentrations were in Clift Sound and around

the Scalloway Islands (42% of the total), between Cat Firth and Dales Voe (19%), and in Olna Firth (8%). The

largest concentration away from aquaculture sites was in northern Sullom Voe (3%).

5. Winter counts of seaduck and diving seabirds

Surveys by boat in Yell Sound and Sullom Voe in January and December recorded similar numbers to recent

winters, the most numerous species being European Shag (891 in January, 1052 in December), Black Guillemot (492, 371), Great Cormorant (465, 579), and Red-breasted Merganser (153, 114). Surveys in west

Mainland (February, from land) and east Mainland (December, by boat) also recorded similar numbers to

recent winters.


Only 27 oiled seabirds were found during the year, mostly Fulmars (22), all on the west coast of Shetland and mostly (19) in northwest Mainland in March to July. Eight samples taken of oiled feathers were all typed as

refined fuel oils. No unusually high mortality of any seabird species was detected during the year.

In summary, there was no evidence that the operation of the Sullom Voe Terminal, or its associated

tanker traffic, had any detrimental impact on Shetland’s seabird populations during 2015.

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1.1. Weather Weather can influence the ability to carry out seabird monitoring, and in extreme cases, can directly affect

seabirds’ breeding success.

Persistent westerly swell during much of April restricted the number of mornings available for pre-breeding

counts of Black Guillemots at monitoring sites on the west coast of Shetland, and for the Seabirds Count

census counts of the wider coastline. It was the wettest May on record, and the cold and generally unsettled

weather made for difficult observational conditions at times during the early checks at breeding success plots. By the beginning of June, the cliffs at Troswick Ness and Burravoe (in particular) were the wettest we had

ever seen at that time of year, and this probably affected particular nest sites of Fulmar, Shag and Common

Guillemot. Conditions at Esha Ness were rather windier during plot counts than at the other colonies, but this seemed to have little effect on Fulmar numbers, while persistent swell on the west coasts of Shetland

throughout June restricted surveys by boat to east coasts. Strong south-easterly winds and heavy swell at the

beginning of July, and again at the beginning of the second week of July, disrupted Guillemot fledging, but

after this weather had little impact on seabirds or our monitoring activities.

Table 1.1. Details of observer, date, time, weather and sea conditions for study plot counts of Fulmars, Common Guillemots and Razorbills at four colonies in June 2015.

Sumburgh Head Observer: Martin Heubeck

Date Time (BST) Wind Sea state Cloud cover

3rd June 2015 1330-1530 WSW 4 Moderate swell 3/8

8th June 2015 1345-1545 W 3-4 Calm 2/8

12th June 2015 1315-1515 NW 3 Calm 5/8

13th June 2015 1330-1545 NNE 1-3 Calm 7/8

15th June 2015 1330-1530 NW 3 Calm 6/8

Troswick Ness Observer: Martin Heubeck


2nd June 2015 1000-1445 SE 3-4 Heavy swell 1/8

4th June 2015 1030-1515 SW 4 Calm 4/8

8th June 2015 1000-1140 W 3 Calm 7/8, rain 1045-1105

12th June 2015 1000-1135 NW 3 Calm Drizzle until 1030, then

6/8

15th June 2015 1015-1140 NW 4 Calm 8/8

Esha Ness Observer: Mick Mellor


2nd June 2015 1300-1400 N 2 Moderate swell 5/8

4th June 2015 1300-1400 W 5 Heavy swell 4/8

8th June 2015 1300-1400 NW 3 Moderate swell 4/8

12th June 2015 1300-1400 W 4-5 Moderate swell 5/8

15th June 2015 1300-1400 NW 3-4 Heavy swell 7/8

Burravoe, Yell Observer: Mick Mellor


3rd June 2015 1025-1100 NW 4 Slight swell 5/8

8th June 2015 0950-1030 NW 2 Slight swell 6/8

12th June 2015 0945-1030 NW 3 Calm 8/8

15th June 2015 0950-1030 NW 3 Calm 8/8

18th June 2015 1000-1030 NW 4 Calm 8/8

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1.2a. Northern Fulmar Fulmarus glacialis: Population counts

After a steady increase in 1977-2000, the mean counts of AOS at the four colonies monitored have since fluctuated within a gradual downward trend (Figure 1.1). At Troswick Ness, the mean count of apparently

occupied sites (AOS) was 24% lower than in 2014 and the maximum count 20% lower (Table 1.2); the mean

and maximum counts of adults were 18% and 20% lower, respectively. The cliffs at Troswick were saturated by rain in early June and many nest sites were very wet. On 15th June, a high proportion of adults were sitting

slightly off-site and did not qualify as an AOS, and many of the birds previously scored as AOS may not

actually have been on eggs (see Figure 1.2). The cliffs were equally wet at Burravoe, and counts of AOS were

also rather variable although there was little difference between 2014 and 2015 means.

Table 1.2. Mean counts of Fulmars and apparently occupied sites (AOS) at four Shetland colonies, 2014-2015. Statistics: number of counts, range, mean, standard deviation, coefficient of variation, % change since

2014 and population indices for AOS (1978 = 100).

Colony Unit Year n Range Mean SD CV % ch. Index

Sumburgh Birds 2014 5 276-337 294.0 24.57 0.08

Head 2015 5 249-271 256.0 8.83 0.03 -12.9

0.08 AOS 2014 5 197-238 223.2 16.02 0.07 152.1

2015 5 196-214 202.2 7.03 0.04 -9.4 137.8

Troswick Birds 2014 5 1086-1211 1150.4 50.81 0.04

Ness 2015 5 914-973 946.2 21.88 0.02 -17.8

AOS 2014 5 838-925 890.4 32.10 0.04 144.2

2015 5 583-738 681.6 59.98 0.09 -23.5 110.4

Esha Ness Birds 2014 5 273-433 356.2 66.96 0.19

2015 5 261-431 350.4 63.87 0.18 +1.6

AOS 2014 5 243-289 262.4 21.48 0.08 109.2

2015 5 240-319 284.2 28.27 0.10 +8.3 118.2

Burravoe Birds 2014 5 228-259 242.0 13.06 0.05

2015 5 201-243 218.6 17.36 0.08 -9.7

AOS 2014 5 185-210 196.4 11.15 0.06 210.9

2015 5 170-211 189.8 18.62 0.10 -3.4 203.8

Figure 1.1. Annual index (1978 = 100) of Fulmar apparently occupied sites in study plots at four colonies,

1976-2015 , and the mean index for the four colonies.

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1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014

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Esha Ness

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1.2b. Northern Fulmar Fulmarus glacialis: Breeding success

This was measured by counting chicks present in the population plots in mid August (just before the first is likely to fledge) and dividing the total by number of nest sites scored as an AOS on each of three checks in

late May and early June (the photographic method, adopted in 2012), and also by the mean June count of AOS

(the method used since 1985). Both methods will over-estimate the number of birds actually incubating, and marking individual sites on photographs is intended to minimise this. However, differentiating an AOS from

a non-incubating adult requires judgement by the observer, and errors can be made. An AOS can also be

overlooked, either through observer error or because the incubating adult is partly or wholly hidden by rocks

or vegetation (large chicks can be easier to detect in August because the site is surrounded by faeces and shed down). Also a few birds may not have laid an egg by the time of the three early visits.

Chicks were counted at all colonies on 15-16th August (Table 1.3), and scored as small (still mostly covered in down), medium (c.50% down cover) or large (little down left). Heavy rain overnight and on the morning of

15th meant many chicks were bedraggled and for some it was difficult to distinguish between ‘medium’ and

‘large’ categories.

Table 1.3. The dates of visits to Fulmar plots in 2015, the total number nest sites scored as AOS on one or

more of three checks in late May and early June, the number scored as an AOS on all three checks, the mean June count of AOS, the number of chicks present in mid August, the number of (extra) sites at which chicks

were present but only qualified as an AOS on one or two of the May/June visits or were overlooked completely,

breeding success ± SE calculated (a) by the marked photograph method (chicks / 3 visits + extra sites), and (b) by the population count method (chicks / mean June count), with 2014 figures in brackets.

Sumburgh Head: 29th May, 1st June, 3rd June, 15th & 16th August

Plot AOS 3 visits Mean Chicks Extra Success a (2014) Success b (2014)

GSG 27 20 19.6 7 0 0.35 (0.31) 0.36 (0.15)

GTS 166 124 143.0 43 1 0.34 (0.61) 0.30 (0.48)

GPN 50 33 38.6 13 0 0.39 (0.65) 0.34 (0.55)

Sum 243 177 201.2 63 1 0.35 (0.59) 0.31 (0.45)

Mean 0.36 (0.52) 0.33 (0.39)

± SE 0.02 (0.11) 0.02 (0.12)

Troswick Ness: 28th May, 2nd June, 4th June, 15th August


Brei Geo 369 261 280.2 53 3 0.20 (0.52) 0.19 (0.45)

Sand. Geo 389.8 68 0.17 (0.43)

Sum 670.0 121 0.18 (0.44)

Mean 0.18 (0.44)

± SE 0.01 (0.01)

Esha Ness: 28th May, 2nd June, 4th June, 15th August


CG 229 143 199.2 56 5 0.38 (0.40) 0.28 (0.32)

MC 38 20 28.6 9 0 0.45 (0.47) 0.31 (0.30)

FG 56 34 52.0 16 1 0.46 (0.28) 0.31 (0.23)

Sum 323 197 279.8 81 6 0.40 (0.39) 0.29 (0.30)

Mean 0.43 (0.38) 0.30 (0.28)

± SE 0.03 (0.06) 0.01 (0.03)

Burravoe: 29th May, 1st June, 3rd June, 15th August


227 150 189.8 72 13 0.44 (0.54) 0.38 (0.43)

At Sumburgh Head, 73% of sites scored as AOS at least once qualified as AOS on each of the three early

checks (67% in 2014). Persistent rain on 15th August limited the count of chicks to the largest plot (which can

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be viewed from a vehicle), the other two plots being checked the following morning. Only one ‘extra’ chick

was recorded, at a site that had been scored incorrectly as ‘2 adults’ on the first check in May. Although 59%

of chicks were scored as ‘large’ (mostly clear of down), none were believed to have fledged, and no dead chicks were seen. Mean breeding success by the photographic method was 31% lower than in 2014, and there

was little difference between the three plots.

At Troswick Ness, population counts are conducted at two large geos 200 m apart, but photographs are only

used to assess breeding success at Brei Geo due to time constraints. On the early checks, the cliffs were the

wettest in memory (i.e. since 1978) for that time of year, and many vacant and AOS sites were marked as

‘wet’; of sites qualifying as an AOS at least once, 71% were marked as an AOS on all three checks (74% in 2014). In the population counts, there is a tendency for the number of AOS to decline during the first three

weeks of June, although they generally remain within ± 5% of the mean (Figure 1.2). However, the count at

Troswick Ness was exceptionally low on 15th June 2015 (Figure 1.2), when the number of birds present (958) was slightly higher than the average (946) but many were sitting off-site and clearly not on an egg; it was

suspected that a higher than usual proportion of sites previously scored as AOS actually had no egg. On 15th

August, chicks were present at three ‘extra’ sites, two of which had had adults present on all the early checks

but were scored wrongly, and one had been overlooked on the second check. Of the 53 chicks at Brei Geo, 53% were scored as ‘large’, while one ‘medium’ chick was freshly dead off-site with no sign of injury or

scattered feathers; breeding success by the photographic method was 62% lower than in 2014, and 60% lower

at Sandvis Geo using the mean of the population counts.

Figure 1.2. Counts of Fulmar AOS at Troswick Ness, plotted as a percentage of the mean of the series of five counts that year, against count date. Trend lines for 2013 and 2014 are identical.

At Esha Ness, 61% of sites qualifying as AOS at least once were scored AOS on all three early checks (62% in 2014). Of the six sites with ‘extra’ chicks in August, five (1 small, 3 medium, 1 large chick) were either

overlooked or actually had no adults present on the first check on 28th May; only 37% of the total of 81 chicks

were scored as ‘large’ and has been suspected in previous years, some breeders at Esha Ness might not have laid by the time of the first check. Breeding success was slightly higher (by 13%) than in 2014.

At Burravoe, 66% of sites qualifying as AOS at least once were scored AOS on all three early checks (65% in 2014). The Burravoe plot is largely a rather featureless, grassy slope and probably the easiest of the colonies

to overlook birds at. Of the 13 ‘extra’ sites, four had adults present and were scored wrongly, while nine were

either overlooked or genuinely had no adults present, six on the first check (3 medium, 3 large chicks).

Breeding success was 19% lower than the rather high figure derived in 2014.

Mean success at the four colonies was 27% lower than in 2014 by the photographic method, and 28% lower

by the mean June count method (Figure 1.3).

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Figure 1.3. Mean Fulmar breeding success (± SE) at 3-4 monitored colonies, 1985-2015 (Burravoe from 2003 only), calculated as the number of chicks present in mid-August divided by the mean of five counts of

apparently occupied sites (AOS) in June (black), and by the number of sites qualifying as AOS on each of

three dates in late May and early June (red).

0.10

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1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016

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1.3a. European Shag Phalacrocorax aristotelis: Population counts

Counts of nests and adults were made from land at No Ness and Sumburgh Head, but sea conditions along the western coasts of Shetland, and boat availability, limited counts from the sea to the southeast Mainland and

Mousa, surveyed on 19th and 20th June (Table 1.4). As is 2014, a high proportion of nests were active.

However, no chicks were seen in 2014 along the coast from Virkie north to Mousa whereas in 2015 most nests contained large chicks (some fully feathered and wandering away from nests), despite the count dates only

being four days later, indicating considerably earlier laying in 2015.

Table 1.4. Counts of Shag nests (trace, empty, and active, i.e. apparently incubating or containing chicks) in

June along coasts surveyed in 2015, the percentage of nests that were active, and count date. At No Ness and

Sumburgh Head, where more than one count from land was made in a year the highest nest total is given (*).

Coastline 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Mousa (sea) 71

90% 12/6

94

89% 20/6

109

86% 21/6

113

97% 22/6

26

62% 25/6

52

94% 16/6

65

100% 20/6

No Ness (land) 125* 78% 27/5

110* 76% 1/6

124* 83% 14/6

139* 97% 13/6

150* 95% 22/6

138* 94% 13/6

185* 89% 23/5

204* 95% 9/6

134* 84% 27/5

54* 48% 12/6

49* 47% 10/6

89 87% 12/6

89 93% 16/6

No Ness (sea) 144 94% 12/6

177 79% 20/6

207 94% 4/6

271 97% 21/6

295 98% 22/6

80 44% 25/6

153 88% 16/6

160 87% 20/6

Cumlewick Ness (sea)

10 100% 12/6

13 77% 20/6

14 93% 4/6

13 100% 21/6

12 100% 22/6

11 64% 25/6

11 82% 16/6

9 100% 20/6

Troswick to Virkie (sea)

122 89% 12/6

114 86% 20/6

149 93% 4/6

165 96% 13/6

167 96% 16/6

61 38% 26/6

91 91% 15/6

108 93% 19/6

Sumburgh Head (land)

221* 95% 6/6

207* 86% 27/5

166* 83% 5/6

233* 97% 13/6

213* 99% 22/6

219* 95% 31/5

223* 93% 16/6

290* 97% 8/6

100* 67% 27/5

85* 54% 30/5

73* 33% 10/6

115 85% 9/6

114 92% 13/6

Total (from sea

at No Ness)

568 93%

564 84%

734 94%

877 97%

251 42%

422 89%

456 92%

At Sumburgh Head, after three years of extensive non-breeding in 2011-13, nest counts in 2014-15 appear to

have stabilised at around half of the numbers recorded throughout most of the 2000s (Figure 1.4). In the longer term, breeding numbers at Sumburgh Head declined by c.40% for unknown reasons between 1988 and 1992,

the summer before the Braer oil spill in January 1993. Counts during this period were also notable for the

large number of adults present at the colony, standing around in breeding areas and roosting on low rocks near

the water’s edge. Along the coast between Virkie and Mousa, non-breeding was also evident in 2013 but the nest count in 2015 was only 5% below the average in 1993-2005 (mean 349, range 316-390) although 40%

lower than the counts in 2009 and 2010.

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Figure 1.4. Counts of adult Shags and nests at Sumburgh Head (from land; roosting adults were not counted

in 1988 and 1999) and along the coast from Virkie north to Mousa (from the sea; excludes Cumlewick Ness

which was first counted in 1999).

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1.3b. European Shag Phalacrocorax aristotelis: Breeding success This was monitored in the usual plots at Sumburgh Head (6th April to 25th August, 25 checks), and Burravoe,

Yell (8th April to 25th August, 31 checks). At the former, it was one of the earliest breeding seasons in the past

20 years, with a 40- to 50-day shift in timing of laying since 2013 (Figure 1.5). Breeding numbers at Sumburgh Head were similar to 2014, but half that recorded in the same plots in 2010 (Table 1.5). The proportion of

nests that progressed to incubation and at which chicks were seen were both high, and while there was some

brood reduction (7 chicks from 7 nests, one seen dead) and complete losses of broods (6 nests, at least 7

chicks), breeding success at 1.41 fledged per laying pair was well above the 1988-2014 mean of 1.12 (Figure

1.6). Two late broods fledged by 1st-5th and 5th-10th September, respectively.

Figure 1.5. The estimated dates by which 25%, 50% and 75% of apparently incubating Shag nests were first

recorded as such in study plots at Sumburgh Head, 1996-2015. In years when none were incubating on the first visit, the date of first recorded incubation is also shown.

Table 1.5. Shag breeding success at Sumburgh Head and Burravoe: the number of former nest sites where an adult(s) but no nest material was recorded (Ad.), the number of trace (Tr.), well-built but empty (AON), and

incubated nests (Inc.), the percentage of all nests which progressed to incubation (% Inc.), the percentage of

incubating nests at which chicks were recorded (% H.), the percentage of incubating nests from which no chicks fledged (Fl. 0), the number of chicks fledged (Ch.), mean brood size at fledging (Brood), and sum

breeding success (Succ.: Ch./Inc.).

Sumburgh Head (14 plots)

Year Ad. Tr. AON Inc. % Inc. % H. Fl. 0 Ch. Brood Succ.

2008 14 12 6 182 91.5 74.7 27.5 274 2.08 1.51

2009 13 17 4 185 89.8 76.8 28.6 250 2.05 1.58

2010 3 23 12 222 86.4 73.0 41.0 274 2.09 1.23

2011 26 21 11 141 82.1 22.5 83.0 43 1.79 0.30

2012 51 21 14 96 73.3 30.2 76.0 36 1.57 0.38

2013 36 15 27 56 57.1 16.1 83.9 15 1.67 0.27

2014 25 2 2 108 96.4 67.6 36.1 132 1.91 1.22

2015 10 5 3 111 93.3 76.6 28.8 157 1.99 1.41

Burravoe, Yell (3 plots)

2012 - 6 2 36 81.8 52.8 50.0 26 1.44 0.72

2013 2 2 1 39 92.9 64.1 46.2 36 1.71 0.92

2014 6 4 2 27 81.8 81.5 25.9 42 2.10 1.56

2015 2 2 0 35 94.6 54.3 51.4 28 1.65 0.80

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Figure 1.6. Shag breeding parameters at Sumburgh Head, 1988-2015. Upper: chicks fledged per incubated

nest. Lower: The percentage of: (i) nests that progressed to incubation (blue), (ii) incubating nests where

chicks were recorded (red), (iii) laying pairs that fledged a brood of three chicks (green).

With breeding success having been monitored at Burravoe since 2012, differences in phenology between there

and Sumburgh Head can now be better described (Table 1.6), although the disparity in sample sizes should

be noted; the greatest difference between the two colonies in timing of laying was of 5-6 weeks in 2013. Although incubation was recorded at a high proportion of nest sites at Burravoe in 2015, chicks were seen in

a much lower proportion of nests than at Sumburgh (Table 1.5). Only one case of brood reduction was

recorded (a b/3 to b/2) and only two broods were known to have been lost (at least 2 chicks, one seen dead), but only one brood of three fledged. A ¾-grown chick was still present in one nest on the last check, on 25th

August, and was assumed to have fledged; breeding success was 0.80 fledged per laying pair. Although it

cannot be quantified, it was felt that nest sites may have been more affected by the heavy rain in May than at

Sumburgh Head due to the nature of the cliff topography; many nests at Burravoe are on narrow rock ledges below a high (waterlogged) grassy cliff, and water continued to stream down and across these ledges long

after rain had stopped, whereas most nests at Sumburgh are in more open situations and could dry out between

spells of rain.

Table 1.6. The estimated dates by which 25%, 50% and 75% of apparently incubating Shag nests were first

recorded as such in study plots at Sumburgh Head (SH) and Burravoe (BRV), 2012-15.

Colony SH BRV SH BRV SH BRV SH BRV

Year 2012 2012 2013 2013 2014 2014 2015 2015

25% 9/5 7/5 21/5 12/4 7/5 25/4 9/4 -

50% 28/5 15/5 9/6 25/4 20/5 9/5 17/4 9/4

75% 2/7 20/5 26/6 3/5 2/6 25/5 28/4 14/4

Sample size 96 36 56 39 108 27 111 35

0.00.20.40.60.81.01.21.41.61.8

1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014

0

20

40

60

80

100

1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014

12

1.4a. Black-legged Kittiwake Rissa tridactyla: Population counts

Sea conditions on Shetland’s west coasts, and boat availability limited counts to the southeast Mainland, where the total number of nests was 18% lower than in 2014 (Table 1.7). These breeding stations are completely

sheltered from westerly swell and have been counted more frequently than those along more exposed coasts

(Figure 1.7). On the baseline survey in 1981, there was a total of 18 discrete colonies at No Ness, Troswick Ness and Boddam, and despite a decrease of 93% in the total number of nests 12 of these colonies were still

occupied in 2015 (7/10 at No Ness, 2/3 at Troswick, 3/6 at Boddam), six of which held eight or fewer nests.

One can only speculate on whether breeding in such small groups, with a consequent reduction in social

stimulation, is affecting breeding performance in this highly colonial species.

During the Eider census, a new breeding station was found on 1st August at Neeans (GR HU267592: 23 adults,

25 used nest sites, 3 large chicks), west of Vementry on the south coast of St Magnus Bay. It is unlikely this would have been overlooked on the 2012 Eider census, and almost certainly represents a shift of breeding

adults from the long-established colony at the Murbie Stacks, Muckle Roe (5 km to the northeast), which was

still occupied in 2011 (29 adults, 21 nests) but has been deserted for the past two summers (Jim Dickson, pers.

comm.).

Table 1.7. Counts of Kittiwake nests (incubating, empty and trace) and adults (excluding roosts) at breeding stations surveyed in 2015, compared with counts in 1981 (used as a baseline), and from 2006.

SE Mainland 1981 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Mousa 148 nc 16 14 0 0 0

No Ness 1768 251 269 314 165 175 139

Troswick Ness 716 63 61 27 19 21 22

Boddam 256 28 35 37 20 20 18

The Taing, Exnaboe 0 0 0 0 0 1 0

Total nests 2888 342 381 392 204 217 179

% change p.a. -6.0 +3.7 +2.9 -19.6 +6.4 -17.5

Total adults 3944 448 511 468 309 238 288

Figure 1.7. The total number of Kittiwake nests at breeding stations in southeast Mainland, 1981-2015.

0

500

1000

1500

2000

2500

3000

198

1198

2198

3198

4198

5198

6198

7198

8198

9199

0199

1199

2199

3199

4199

5199

6199

7199

8199

9200

0200

1200

2200

3200

4200

5200

6200

7200

8200

9201

0201

1201

2201

3201

4201

5

Mousa

No Ness

Troswick

Boddam

13

1.4b. Black-legged Kittiwake Rissa tridactyla: Breeding success

This was monitored at the same six colonies as in 2013 and 2014, with first checks being made between 9th May (Sumburgh Head) and 19th May (Ramna Geo, Burra). Although there is a bias in SOTEAG coverage

towards colonies around the south Mainland, Kittiwake breeding success is also monitored at Fair Isle (FIBO),

Foula (Foula Ranger Service), and Noss and Hermaness (SNH).

Laying was earlier and more synchronous between colonies than in 2011-14, with median laying date

averaging nine days earlier than in 2014 (Table 1.8, Figure 1.8). The total number of nests monitored (367,

including trace nests) was 15% lower than in 2014, and sample sizes are now very low at Compass Head and No Ness, where most nests are not visible from the cliff-top (Table 1.9). The proportion of nests that

progressed to incubation exceeded 80% at all but Compass Head (59%) and Hich Holm (68%) off St Ninian’s

Isle, and chicks were also seen in over 60% of incubated nests at all but Compass Head (23%) and Hich Holm (0%). At Hich Holm, 90% of breeding attempts had failed by 14th June and 100% by 23rd June, whereas 12

km to the north only 13% of attempts at Ramna Geo had failed by 22nd June. This difference was almost

certainly due to some form of disturbance, and the Hich Holm colony (which had a successful season in 2014,

but is on an open cliff face and was deserted for several years in the early 2000s) has almost certainly been ‘rediscovered’ by Great Skuas, although none were actually seen predating the colony.

Table 1.8. Dates by which 20%, 50% and 80% of Kittiwakes had laid at monitored colonies, 2013-2015.

Sumburgh Head Compass Head No Ness

2013 2014 2015 2013 2014 2015 2013 2014 2015

20% 1/6 26/5 20/5 31/5 30/5 17/5 31/5 31/5 24/5

50% 6/6 2/6 24/5 6/6 8/6 25/5 4/6 3/6 26/5

80% 11/6 9/6 30/5 10/6 16/6 31/5 5/6 7/6 31/5

Hich Holm, St Ninian’s Ramna Geo, Burra Burravoe, Yell

2013 2014 2015 2013 2014 2015 2013 2014 2015

20% 3/6 28/5 20/5 6/6 30/5 24/5 27/5 29/5 22/5

50% 7/6 4/6 25/5 10/6 5/6 29/5 3/6 2/6 27/5

80% 14/6 10/6 29/5 15/6 10/6 3/6 8/6 9/6 1/6

Figure 1.8. Dates by which 50% of Kittiwakes breeding that year were presumed to have laid their first eggs

at colonies monitored by SOTEAG, 1989-2015.

10

15

20

25

30

35

40

45

1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015

Days f

rom

1st

May

Burravoe, Yell Esha Ness Clett Head, Whalsay

Westerwick Ramna Geo, Burra Kettla Ness

St Ninian's isle No Ness Troswick Ness

Compass Head Sumburgh Head

14

Table 1.9. The number of Kittiwake nests and occupied sites at monitored colonies 2006-2015; the percentage

of: (i) all nests at which incubation was recorded or assumed, (ii) incubating nests in which at least one chick

was known to have hatched, (iii) hatched nests in which two chicks were seen, (iv) nests where young hatched in which one or more dead chicks were seen, (v) incubating nests that failed; the number of young fledged;

breeding success (young fledged per incubating nest). Mean and standard error are also given for plots at

Sumburgh Head; all visible nests are monitored at the other colonies.

Sumburgh Head 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Total nests 156 163 148 177 177 145 139 138 150 135

Incubating 144 128 89 128 151 94 93 89 115 117

% Incubating 92.3 78.0 60.1 72.3 85.3 64.8 66.9 64.5 76.7 86.7

Sites adult(s) only 4 20 36 39 22 39 35 40 29 21

% Nests hatched 89.6 82.8 21.3 80.5 86.8 21.3 60.2 32.6 85.2 59.8

% Nests hatched b/2 34.1 17.9 5.3 24.3 11.5 15.0 1.8 0 46.9 2.9

% Hatched with dead 8.5 12.3 5.3 3.9 8.4 10.0 26.8 20.7 2.0 2.9

% Nests failed 26.4 46.9 98.9 44.5 88.1 100 84.9 100 20.9 71.8

Chicks fledged 125 69 1 75 18 0 14 0 132 33

Sum success 0.87 0.54 0.01 0.59 0.12 0 0.15 0 1.15 0.28

Mean success 0.70 0.47 0.51 0.11 0 0.13 0 1.20 0.19

SE 0.14 0.08 0.09 0.06 0.04 0.10 0.06

Compass Head 2008 2009 2010 2011 2012 2013 2014 2015

Total nests 61 62 55 21 24 21 23 22

Incubating 37 41 41 10 18 13 15 13

% Incubating 60.7 66.1 74.5 47.6 75.0 61.9 65.2 59.1

Sites adult(s) only 3 5 2 6 8 5 2 4

% Nests hatched 13.5 65.9 73.2 30.0 38.9 30.8 60.0 23.1

% Nests hatched b/2 0 17.9 13.3 0 14.3 0 55.5 0

% Hatched with dead 0 14.3 53.3 0 0 50.0 0 0

% Nests failed 100 56.1 100 100 88.9 100 40.0 92.3

Chicks fledged 0 19 0 0 3 1 14 1

Sum success 0 0.46 0 0 0.17 0.08 0.93 0.08

No Ness 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Total nests 30 31 43 45 50 29 22 19 17 14

Incubating 26 23 32 39 38 21 16 14 14 13

% Incubating 86.7 74.2 74.4 86.7 76.0 72.4 72.7 73.7 82.4 92.9


% Nests hatched 84.6 87.0 40.6 74.4 50.0 38.1 31.3 0 71.4 61.5

% Nests hatched b/2 27.3 10.0 0 34.5 15.8 0 0 0 60.0 0

% Hatched with dead 13.6 15.0 7.7 6.9 5.3 0 20.0 0 0 0

% Nests failed 26.9 82.6 75.0 51.3 100 100 100 100 35.7 92.3

Chicks fledged 20 4 8 23 0 0 0 0 15 1

Sum success 0.77 0.17 0.25 0.56 0 0 0 0 1.07 0.08

Hich Holm 2013 2014 2015

Total nests 58 61 61

Incubating 38 54 41

% Incubating 67.9 88.5 68.3

Sites adult(s) only 5 6 5

% Nests hatched 13.2 77.8 0

% Hatched b/2 0 61.9 -

% Hatched with dead 0 0 -

% Nests failed 100 27.8 100

Chicks fledged 0 64 0

Sum success 0 1.19 0

15

Table 1.8. continued.

Ramna Geo, Burra 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Total nests 110 124 91 111 117 76 64 48 68 37

Incubating 101 100 55 81 74 45 24 34 64 30

% Incubating 91.8 80.6 60.4 73.0 63.2 59.2 37.5 70.8 94.1 81.1


% Nests hatched 84.2 80.0 16.9 85.2 18.9 2.2 0 35.3 6.2 66.7

% Hatched with b/2 22.4 30.0 10.0 62.3 7.1 0 0 0 0 0

% Hatched with dead 1.2 7.5 0 0 14.3 0 0 8.3 0 5.0

% Nests failed 22.5 30.0 83.1 17.3 98.6 100 100 70.6 100 93.3

Chicks fledged 94 80 11 103 1 0 0 10 0 2

Sum success 0.92 0.80 0.19 1.27 0.01 0 0 0.29 0 0.07

Burravoe, Yell 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Total nests 89 104 98 113 135 117 128 130 114 98

Incubating 80 94 85 99 107 87 94 99 95 84

% Incubating 89.9 91.0 86.7 87.6 79.3 74.4 73.4 76.2 83.3 85.7

Sites adult(s) only) 1 1 7 4 8 12 9 15 16 14

% Nests hatched 85.0 87.2 34.1 72.7 69.2 28.7 51.1 40.4 76.8 73.8

% Hatched with b/2 30.9 25.6 34.5 51.5 6.8 8.0 43.8 2.5 60.3 13.1

% Hatched with dead 2.9 4.9 0 1.4 8.1 4.0 2.1 15.0 1.4 4.9

% Nests failed 25.0 26.6 72.9 35.4 53.3 78.2 59.6 87.9 32.6 79.8

Chicks fledged 76 81 33 95 52 20 49 12 100 17

Sum success 0.95 0.86 0.39 0.96 0.49 0.23 0.52 0.12 1.05 0.20

Figure 1.9. Mean Kittiwake breeding success (+ SE) at colonies (4-7 per year) monitored by SOTEAG, 1986-

2015. Breeding success is defined as chicks fledged per apparently laying pair.

At the other five colonies, most breeding failures occurred at the late incubation and early chick stages,

suggesting problems with food availability in late June and early July. Thereafter, chick survival improved at

Sumburgh Head with 79% of chicks alive on 14th July going on to fledge, whereas chick mortality continued throughout July at Burravoe (including one dead in the nest on 29th July that was at least 16 days old) and only

44% of chicks alive on 15th July fledged.

At the colonies monitored for SOTEAG, annual Kittiwake breeding success since 1986 has averaged only 0.39 chicks fledged per laying pair, and in only five of the past 30 years has it has equaled or exceeded 0.80,

a minimum level calculated to maintain a closed population (Figure 1.9). Average success in 2015 (0.10 ±

0.03 SE) was the ninth year of 0.10 or lower during this period, and the sixth such year since 2000.

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014

16

1.5a. Common Guillemot Uria aalge: Population counts

In south Mainland, numbers of individual birds in study plots were slightly higher than in 2014 at Sumburgh Head and Troswick Ness (Table 1.10), while in northwest Mainland, a few adults continue to attend the greatly

reduced colony at the Esha Ness cliffs (the mean count in 2000 was 469 birds) but it is unlikely that any breed

there now. In southeast Yell, all birds at the small colony at Burravoe are included in the three study plots, but breeding at one of these (counts of 64-84 birds in 2012) probably ceased in 2013 (3-15 birds), with a few birds

attending the ledges intermittently in 2014 (6-20) and 2015 (0-29). With the exception of years of low colony

attendance in 2011 and 2013, the mean population index at the four colonies has changed little since 2010, at

c.45% of that in 1978 when SOTEAG’s monitoring programme began (counts in 1976-77 were made by the Nature Conservancy) (Figure 1.10).

The annual total count from land at Sumburgh Head (6,957 birds on 13th June) was 7% lower than in 2014 (7,441), but this probably reflected lower colony attendance that day as the plot counts that afternoon were the

lowest in the series of five, and 9% lower than the average for the month (Table 1.10, Figure 1.11).

Table 1.10. Mean counts of individual Common Guillemots in study plots at four Shetland colonies, 2014-

2015. Statistics are: number of counts, range, mean, standard deviation, coefficient of variation, percentage

change since 2014, and population indices (1978 = 100).


Sumburgh Birds 2014 5 758-901 838.4 52.47 0.06 63.2

Head 2015 5 805-951 884.2 62.68 0.07 +5.5 66.7

Troswick Birds 2014 5 246-287 264.2 15.27 0.06 48.1

Ness 2015 5 264-307 286.6 18.09 0.06 +8.5 52.2

Esha Ness Birds 2014 5 8-48 27.4 14.36 0.52 3.9

2015 5 5-32 20.8 11.32 0.54 -24.1 3.0

Burravoe Birds 2014 5 183-225 202.8 15.97 0.08 60.7

2015 5 169-227 196.6 26.43 0.13 -3.1 58.8

Figure 1.8. Annual index (1978 = 100) of Common Guillemot numbers in study plots at four monitored

colonies, 1976-2015, and the mean index for the four colonies.

0

25

50

75

100

125

150

175

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014

Sumburgh

Troswick

Eshaness

Burravoe

Mean

17

Figure 1.11. Comparison of trends in census counts of the Sumburgh Head Common Guillemot colony on a

single date in June, and the mean of the total of five counts in eight study plots.

0

250

500

750

1000

1250

1500

1750

2000

2250

2500

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

To

tal P

lot

Co

un

ts

To

tal C

olo

ny C

ou

nts

Total Colony Counts

Total Plot Counts

18

1.5b. Common Guillemot Uria aalge: Breeding success and chick diet at Sumburgh Head

This was monitored in a single plot on the east side of the Head, which was checked daily from 20th April until 21st July, with the number of adults present at the start of the check being recorded. The normal pre-laying

cyclical pattern of attendance occurred, with 27th April being the last day no birds were present, and 196 on

both 25th and 29th April being the highest counts of adults during the season. (Figure 1.12).

The first eggs (3) were seen on 5th May. Cold, wet and windy conditions made following the progress of laying

a challenge, but median laying date was two days earlier than in 2014 and the last presumed first-egg was

recorded on 1st June (Table 1.11). Observations of mixed pairs (bridled:non-bridled) showed frequent change-overs during incubation and no eggs were recorded as having been abandoned on site, suggesting off-duty

mates were not foraging very far from the colony. Hatching success was relatively high, and of 40 first eggs

that did not hatch, 25 were lost before possible hatching (56% of these pairs relaid), 10 around possible hatching (29-37 days) and five were incubated for > 37 days and assumed infertile (Table 1.12).

Table 1.11. Common Guillemot breeding parameters and success in a study plot at Sumburgh Head, 2006-2015, calculated as young fledged (a) per regularly attended site and (b) per site at which eggs were laid.

2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 Attended sites 163 165 166 169 169 164 163 155 158 153

Sites with egg laid 136 142 137 144 154 142 140 98 122 135

% sites laid 83% 86% 83% 85% 91% 87% 86% 63% 77% 88%

First egg date 8/5 4/5 4/5 2/5 2/5 29/4 4/5 7/5 6/5 5/5

Median laying date 19/5 11/5 16/5 10/5 9/5 9/5 14/5 19/5 16/5 14/5

% Hatched first egg 62% 66% 49% 65% 68% 21% 68% 11% 66% 70%

Chicks fledged 78 80 39 91 78 2 55 0 66 70

Fledged/site 0.48 0.48 0.23 0.54 0.46 0.01 0.34 0.00 0.42 0.46

Fledged/egg 0.57 0.56 0.28 0.63 0.51 0.01 0.39 0.00 0.54 0.52

The first chick was recorded on 6th June, and the first chick-feeding watch was made on 13th June, when there

were 30 chicks in the plot and perhaps twice that number in the surrounding area also observed. Two-thirds

of feeds on 13th and 14th June were of gadids that were almost certainly Norway Pout Trisopterus esmarkii, the remainder being sandeels. Younger chicks had difficulty swallowing the larger gadids and a proportion

were either uneaten or stolen by non-parent adults. The first dead chick was seen on 22nd June at 6 days old

and a further six were seen dead at or near their natal site, including two at 23 days and one at 25 days old. When food is scarce both adults are forced to leave their chick unattended. Some of these neglected chicks are

brooded by neighbours, and the first chick was recorded as having neither parent present on site on 24th June.

By then, Great Black-backed Gulls and Herring Gulls were almost constantly present and were seen taking chicks from the plot and surrounding ledges.

Strong southeasterly winds and heavy swell from 26th June to 2nd July probably delayed some chicks from

fledging and the first (6) were assumed to have fledged on the night of 2nd/3rd July, aged 22-26 days. It is convention to assume that 15-day-old chicks are capable of fledging, but deriving the number that probably

fledged was complicated by the variable state of development of chicks of the same age, the presence of

predatory gulls, and spells of heavy onshore swell. Three chicks aged 15 days or older went missing between the morning and late afternoon (c.16.30 pm) checks and were assumed to have been predated: one aged 15

days on 7th July, a runt aged 23 days on 17th July, and the last surviving chick which disappeared between

14.00 (only three adults present) and 15.45 on 21st July aged 28 days. Six chicks that went missing overnight

were assumed not to have fledged because the sea was too rough, and were probably also predated: one aged 15 days on 23-24th June (no others fledged that night), a runt (still all dark grey) aged 18 days on 4-5th July (no

others fledged), three on 8-9th July aged 17, 24 and 26 days (wind overnight N 7 with very heavy swell), and

one on 20-21st July aged 22 days (the second last present). Adding these latter six chicks to the number assumed to have fledged would raise breeding success from 0.52 to 0.56. As in recent years, chicks were still present

on the west side of the Head after the breeding success plot had been vacated, the last being seen there on 28th

July, with all adults gone on 30th July.

19

Figure 1.12. Upper: The daily number of adults, first eggs, relay eggs, first egg chicks, and relay egg chicks

in the breeding success plot at Sumburgh Head in 2015, and the cumulative number of fledged first-egg chicks

and relay-egg chicks. Lower: The number of eggs and chicks missing from the previous day, or known to have been lost that day.

0

25

50

75

100

125

150

175

200

225

01-May 11-May 21-May 31-May 10-Jun 20-Jun 30-Jun 10-Jul 20-Jul 30-Jul

Adults

0

25

50

75

100

125


Relay egg

First egg

0

25

50

75

100


Relay egg chick

First egg chick

0

25

50

75

100


Cumulative relay egg chick fledged

Cumulative first egg chick fledged

0

2

4

6

8


Lost relay egg chick

Lost first egg chick

Lost relay egg

Lost first egg

20

Table 1.12. Outcome (%) of Common Guillemot breeding attempts in a study plot at Sumburgh Head in

2015.

2011 2012 2013 2014 2015

Number of breeding pairs 142 140 98 122 135

Lost first egg before possible hatching (< 29 D), no relay 31.0 15.0 50.0 11.5 8.1

Lost first egg around possible hatching (29-37 D), or chick died hatching 6.3 2.9 4.1 7.4 7.4

Presumed infertile first egg, incubated 38+ D 0.7 0.7 0.0 2.5 3.7

Lost relay egg before possible hatching (< 29 D) 25.4 7.1 34.7 4.9 7.4

Lost relay egg around possible hatching (29-37 D), or chick died hatching 4.9 2.1 0.0 0.8 0.0

Presumed infertile relay egg, incubated 38+ D 0.7 0.7 0.0 0.8 0.0

First egg chick missing before presumed fledging (< 15 D) 12.0 20.7 11.2 12.3 8.1

First egg chick seen dead 4.2 4.3 0.0 0.0 5.2

First egg chick seen predated 0.7 0.0 0.0 0.8 0.7

First egg chick missing 15+ D, assume predated 2.8 5.7 0.0 2.5 5.9

Relay chick missing before presumed fledging (< 15 D) 8.5 1.4 0.0 3.3 0.7

Relay chick seen dead 1.4 0.0 0.0 0.0 0.0

Relay chick missing 15+ D, assume predated 0.0 0.0 0.0 0.0 0.7

Fledged chick from first egg 1.4 37.9 0.0 50.8 50.4

Fledged chick from relay egg 0.0 1.4 0.0 3.3 1.5

Table 1.13. Details of counts of Common Guillemots in the Sumburgh Head breeding success plot in 2015 (with mean and standard deviation), breeding numbers, derived k values (with mean and standard deviation),

and the deviation of counts in population monitoring plots on the same dates from the monthly mean.

Count date in 2015 3/6 8/6 12/6 13/6 15/6 Mean SD

Time (BST) 1340 1355 1325 1340 1340

Total birds in plot (n) 173 172 153 166 172 167.2 8.41

Total regularly attended sites (a) 153 153 153 153 153

Total breeding pairs (b) 135 135 135 135 135

k-value regular sites (a/n) 0.88 0.89 1.00 0.92 0.89 0.92 0.05

k-value breeding pairs (b/n) 0.78 0.78 0.88 0.81 0.78 0.81 0.04

Population count as % of mean for 2015 108% 106% 95% 91% 100%

Figure 1.13. The Sumburgh Head Common Guillemot population index (black, 1978 = 100), and the mean

number of adults present in the breeding success plot per 100 regularly attended sites (blue) and per 100

breeding pairs (red) on the dates and times of the population counts, 2000-2015.

Adult attendance at the breeding success plot (mean of 124 adults per 100 breeding pairs) on the dates of the five population counts elsewhere around Sumburgh Head was slightly lower than in 2014 (131), giving a

slightly higher k-value (0.81 c.f. 0.76 in 2014) (Table 1.13, Figure 1.13).

25

50

75

100

125

150

175

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Ind

ex (

1978 =

100)

/ R

ati

os

21

Feeding watches were carried out in 2-hour sessions on 13 days at and around the breeding success plot, when

incoming adults were checked by telescope to see if they were carrying a fish, and if so followed until the fish

was presented to a chick. Casual observations of feeds when an adult with a fish wandered into the field of view of the telescope during other checks of the plot were also recorded, but casual observations of incoming

birds were not as these would have been biased towards larger fish visible to the naked eye.

Medium to large gadids (almost certainly Norway Pout Trisopterus esmarkii) were the predominant fish type,

followed by medium to small sandeels (Table 1.14), although the ratio of gadids to sandeels varied from day

to day (Figure 1.14). This was in contrast to 2014, when small to medium presumed Saithe Pollachius virens

predominated, only two of which were seen in 2015. ‘Rockling-type’ gadids were identified by their lobate, unforked tail on larger specimens or by their pot-bellied shape on the smallest specimens, which were held

cross-wise in the bill. Clupeids were identified by their deeply-forked colourless tail and very shiny, silvery

body. A few very small fish could not be assigned to type but were not sandeels, while the unidentified category included one large fish not seen previously that was almost certainly a species of eelpout. Feeding

rates were not determined, but the impression was of less frequent feeds than in 2014. Nevertheless, there were

instances of individual chicks being fed more than once in an hour, involving both sandeels and Norway Pout,

suggesting their parents were not travelling far to forage (Table 1.15). The larger average size of Norway Pout in 2015 compared to the Saithe in 2014 probably contributed to the poor development of some chicks which

could not cope with such large items, e.g. one chick aged 8 days was offered a large pout on 25th June but

could not possibly get it in its bill, was later classed as a runt, and was dead on 1st July.

While sandeels are almost certainly the preferred prey for feeding chicks, since 2007 (at least) Guillemots at

Sumburgh Head would appear to be dependent upon at least one species of gadid of the appropriate age class being available reasonably close to the colony for successful breeding (Figure 1.15).

Table 1.14. The percentages (by number) of fish types fed to Common Guillemot chicks at Sumburgh Head on 13 2-hour feeding watches, 13th June to 6th July (n = 452), and seen casually by telescope during checks of

the breeding success plot (n = 63).

Figure 1.14. The percentage of prey items of different fish families fed to Common Guillemot chicks on feeding watches on 13 dates in 2015 (n = 452), casually during checks of the success plot (n = 63), and the

total (n = 515).

0%

20%

40%

60%

80%

100%

13-J

un

14-J

un

15-J

un

16-J

un

17-J

un

18-J

un

19-J

un

20-J

un

21-J

un

22-J

un

23-J

un

24-J

un

25-J

un

26-J

un

27-J

un

28-J

un

29-J

un

30-J

un

01-J

ul

02-J

ul

03-J

ul

04-J

ul

05-J

ul

06-J

ul

Casu

al

TO

TA

L

% Unident.

% Clupeidae

% Gadidae

% Sandeel

Fish type Small Medium Large Total

Sandeel 12.0 (62) 25.0 (129) 5.2 (27) 42.3 (218)

‘Norway Pout-type’ gadid 1.7 (9) 28.9 (149) 19.2 (99) 49.9 (257)

‘Rockling-type’ gadid 4.3 (22) 0 0 4.3 (22)

‘Saithe-type’ gadid 0.2 (1) 0.2 (1) 0 0.4 (2)

Clupeid 0.6 (3) 0.8 (4) 0.2 (1) 1.6 (8)

Unidentified/other but not sandeel 1.2 (6) 0.2 (1) 0.2 (1) 8 (1.6)

22

Table 1.15. Instances of Common Guillemot chick feeds 60 minutes or less apart. These are minima, as some

chicks may have received additional feeds un-noticed.

Date Chick (age) Feeds (time and fish type) 22/6 23 (12 d) 1015 small sandeel; 1054 small sandeel; 1135 medium sandeel

23/6 14B (6 d) 1030 small pout; 1101 large pout

23/6 9A (6 d) 1020 small sandeel; 1105 small sandeel

25/6 25 (12 d) 1359 medium sandeel; 1419 medium pout

25/6 13A (14 d) 1403 medium sandeel; 1450 medium sandeel

25/6 55 (17 d) 1409 medium pout; 1506 small sandeel

29/6 8 (16 d) 0858 small sandeel; 0958 large ‘eelpout’ type

29/6 74 (12 d) 0921 large pout; 1013 large pout

1/7 78B (19 d) 1108 fed medium pout by neighbour; 1152 fed small sandeel by parent

3/7 3 (20 d) 1220 small rockling; 1244 small rockling

5/7 8 (22 d) 1055 small pout; 1128 medium pout

6/7 76 (3 d) 0953 small sandeel; 1008 small sandeel; 1034 medium sandeel

Figure 1.13. Guillemot chick diet (% of feeds) at Sumburgh Head, 2007-15. Sample sizes: 2007 = 324; 2008

= 140; 2009 = 250; 2010 = 250; 2012 = 401; 2014 = 629; 2015 = 515. Too few chicks survived long enough in 2011 and 2013 for meaningful observations.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2007 2008 2009 2010 2011 2012 2013 2014 2015

Unidentified

Squid

Cottidae

Clupeidae

Pipefish

Gadidae

Sandeel

23

1.5c. Common Guillemot Uria aalge: Breeding success at Burravoe, Yell

This was monitored in the same plot as in 2012-14. Because viewing distances from three safe vantage points are greater than at Sumburgh Head, the presence of an egg is more difficult to confirm, and sites at which eggs

were assumed to have been laid were defined as those where an adult was sitting tight (ST) throughout the

visit on two consecutive dates (Table 1.16, a). Other sites where an adult was sitting tight on one or more non-consecutive dates from the date of first assumed laying to 30th June (Table 1.16, b), or where adults were only

ever recorded as standing upright on two or more dates (Table 1.16, c) are listed separately. An incubation

period of 32 days and a minimum fledging period of 15 days were used to calculate breeding success, while

the state of plumage development of chicks that were seen well was also used as a guide to their probable age.

The first bird was assumed to be incubating on 5th May and the first (2) eggs were seen on 8th May. Of the 97

sites where incubation was assumed, eggs were seen on the first such date at 49 sites, and confirmed later in incubation at a total of 90 (93%) sites. Incubation was assumed at 27% of sites by 14th May and 62% by 17th

May, suggesting a median laying date of 16th May, just two days later than at Sumburgh Head. Heavy rain in

late May was believed to have caused substantial egg loss, with most ledges saturated to some degree and

water streaming down the cliff on 1st June. Eggs were lost from at least 15 sites between 24th May and 1st June, with only four known relays, from which two chicks fledged. Eggs were lost from a further nine sites between

8th and 12th June, for unknown reasons.

It is difficult to determine hatching success accurately at Burravoe because of viewing distance, but chicks

were seen at 51 sites. Of these, 49 were known to have survived beyond 15 days (and most to at least 20-25

days), giving breeding success of 0.51 per laying pair. Predatory gulls do not seem to be a problem for Guillemots breeding at Burravoe, and chick survival in the four years breeding success has been monitored

there has undoubtedly been higher than at Sumburgh Head. Of 31 chick feeds noted between 15th June and

19th July, 14 were of sandeels (5 large, 9 medium), 16 were gadids (10 large, 5 medium, 1 small), and one was

undetermined, suggesting a similar diet to that recorded at Sumburgh Head.

Table 1.16. Details of Common Guillemot breeding success monitoring at Burravoe in 2012-15. Adults sitting tight (ST) on two or more consecutive checks (a) were assumed to be incubating. Those sitting tight on just

one, or on two or more non-consecutive checks (b) were assumed not to have laid an egg, although a second

measure of breeding success includes these sites.

2012 2013 2014 2015

Date range visited 8/5 – 27/7 2/5 – 8/8 12/5 – 6/8 5/5 – 10/8

Checks (mean interval in days) 26 (3.2 d) 30 (3.4 d) 27 (3.2 d) 27 (3.6 d)

Date first egg seen / assumed incubation 8/5 16/5 12/5 5/5

ST 2+ checks, assumed laid (a) 115 75 90 97

ST 1 check only from first egg to 30/6 (b) 11 17 19 9

Other regularly attended sites (c) 3 38 34 29

% laid (a/a+b+c) 89.1% 57.7% 62.9% 71.9%

Sites where chicks were seen 62 30 57 51

Minimum % hatched 53.9% 40.0% 63.3% 52.6%

Date first assumed fledged 30/6 – 2/7 8 - 11/7 30/6 – 3/7 29/6 – 3/7

Number assumed fledged (d) 59 27 55 49

Success (d/a) 0.51 0.36 0.61 0.51

Success (d/a+b) 0.47 0.29 0.50 0.46

24

1.6a. Razorbill Alca torda: Population counts

Counts at the Sumburgh Head study plots were less variable than in 2014, with little difference in the means for the two years (Table 1.16). The annual total colony count at Sumburgh Head was 19% lower than in 2014

(Table 1.17), but as with Common Guillemot the plot counts that day were the lowest in the series for the

month. These whole-colony counts are usually conducted on a day of very light wind in order to minimise telescope shake and to access vantage points safely, but a day of low colony attendance cannot be forseen.

Numbers at the other three colonies monitored remain too low for meaningful year-to-year comparisons, but

the overall population index suggests little change since 2007 (Figure 1.16).

Table 1.16. Mean counts of individual Razorbills in study plots at four Shetland colonies, 2014-2015.

Statistics given are: number of counts, range, mean, standard deviation, coefficient of variation, percentage change since 2014, and population indices (1978 = 100).


Sumburgh Birds 2014 5 63-120 91.0 21.08 0.23 31.4

Head 2015 5 71-99 86.6 10.83 0.13 -4.8 29.9

Troswick Birds 2014 5 4-8 6.2 1.79 0.29 29.5

Ness 2015 5 5-12 8.6 3.05 0.35 +38.7 41.0

Esha Ness Birds 2014 5 4-11 7.2 2.86 0.40 9.9

2015 5 0-11 4.2 4.09 0.97 -41.7 5.8

Burravoe Birds 2014 5 8-11 10.2 1.30 0.13 85.0

2015 5 8-17 10.8 3.70 0.34 +5.9 90.0

Figure 1.16. Annual index (1978 = 100) of Razorbill numbers at Sumburgh Head and Esha Ness, 1976-2015,

and the mean of indices at these two colonies plus Troswick Ness and Burravoe.

Table 1.17. Whole colony counts from land of Razorbills at Sumburgh Head. In 2007, an additional 32 birds

were counted from the sea on 7th June in areas judged not to be visible from the cliff top.

0.0

20.0

40.0

60.0

80.0

100.0

120.0

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014

Sumburgh Head

Esha Ness

Mean of 4 colonies

2001 6/6/07 18/6/08 16/6/09 8/6/10 19/6/11 11/6/12 10/6/13 9/6/14 13/6/15

626 199 197 192 133 204 189 151 181 146

25

1.6b. Razorbill Alca torda: Breeding success at Sumburgh Head

This was monitored for the fifth successive year, using the same marked photographs and adding on new nest sites as they became apparent. The presence and number of attending adults at potential nest sites was recorded

and pairs were assumed to have laid an egg if an adult was recorded as sitting tight (ST) on two consecutive

checks (Table 1.19). An incubation period of 35 days, a minimum fledgling period of 15 days, and the state of chick plumage development were all used to help assess probable hatching periods, chick ages, and whether

they could have fledged or not. The nest sites monitored were scattered around different areas of the Head

where Razorbills could be seen reasonably closely using a telescope at a safe vantage point, and it would be

spurious to clump them into ‘plots’.

Birds were sitting tight at two sites on the first check on 6th May, but not on the second check on 9th May,

when birds were assumed to have laid at four other sites. Since incubating Razorbills do not interact with neighbouring birds, confirming the presence of an egg is more difficult than for Common Guillemots.

Hoewever, patient watching confirmed the presence of an egg at 76% of the 67 sites where birds were sitting

tight on two or more consecutive checks, and chicks were seen at 60% of these sites. Only two chicks went

missing before they could have been 15 days old (one at 13 D, one at 7-13 D), and one present on the last check on 2nd August was 17-21 days old and was assume to have fledged. Breeding success was therefore

calculated at 0.57 (38/67), slightly higher than in 2014.

Only two chick feeds were observed, a medium sandeel on 17th June and a large sandeel (swallowed with

difficulty) on 23rd June.

Table 1.19. The number, status and outcome of Razorbill breeding sites monitored at Sumburgh Head, 2011-

15. Adults sitting tight (ST) on two or more consecutive checks were assumed to be incubating. Those sitting

tight on just one, or on two or more non-consecutive checks were assumed not to have laid an egg, although a second measure of breeding success includes these sites.

2011 2012 2013 2014 2015

Date range visited 4/5–11/7 3/5–26/7 3/5–6/8 7/5-26/7 6/5-6/8

Checks (mean interval in days) 22 (3.2) 42 (2.0) 41 (2.4) 26 (3.1) 38 (2.4)

First egg seen / assumed incubation 4/5 3/5 8/5 7/5 9/5

ST 2+ checks, no egg seen (a) 15 25 25 35 16

Egg seen (b) 32 29 18 23 51

Breeding pairs (a + b) 47 54 43 58 67

ST 1 check only from first egg to 30/6 (c) 10 5 15 10 15

Other attended sites 6 7 14 19 14

Sites where chicks were seen 7 38 13 32 40

Date first assumed fledged None 27-28/6 16/7 21-25/6 23-30/6

Chicks assumed to have fledged (d) 0 30 10 30 38

Success (d/a+b) 0.00 0.56 0.23 0.52 0.57

Success (d/a+b+c) 0.00 0.51 0.17 0.44 0.46

26

2. Pre-breeding counts of Black Guillemots Cepphus grylle

Monitoring logistics and constraints Counts are only attempted in conditions of little onshore swell, little or no wind or (at most) a light to moderate

offshore breeze, and no precipitation. Ideally two counts of each coastal section are made each year, but this

is not always possible. Birds ashore are flushed onto the sea where they join displaying groups and can be readily counted, but their willingness to leave cliff perches varies from day to day, and diminishes by early

May, when fieldwork stops. After about 09.00 BST birds tend to disperse to feed, but the timing of this varies,

with birds occasionally departing the colony area unusually early. Some counts are therefore ‘better’ than

others, either because of sea conditions or the birds’ behaviour. In 2015, because census work was also planned (see Appendix 3) it was decided not to attempt second counts unless the first was suspect, but in the event

adverse weather conditions prevented any being made.

The 2015 counts

The single count at Ronas Voe, on 10th April in good conditions, was virtually the same as the most recent in

2013, but 22% lower than the three counts made in 2010-11. A westerly swell at Hillswick Ness on 20th April

had developed unexpectedly overnight, and it was thought that some birds were either not attending sites that morning or had left early. The Ness is walked counter-clockwise and numbers in the northwest sector (slight

swell) were 11% lower than in 2014, 32% lower in the southwest sector (moderate to heavy swell), and 36%

lower in the southeast sector (completely sheltered).

Table 2.1. Counts of adult Black Guillemots at colonies, 2006-15. Counts in brackets were the only ones made that year, those not in brackets were the higher of two. Counts in bold were made in favourable conditions,

those not in bold may have been low (*or definitely were low) because of adverse conditions, or because birds

were difficult to flush from cliff perches. Percentage change is from 2014, or 2013**.

Figure 2.1. Counts of adult Black Guillemots in northwest Mainland, at Hillswick Ness (black) and Ronas

Voe (blue), 1983-2015. Open symbols indicate the lower count when two were made in a year.

0

50

100

150

200

250

300

1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014

West Coast 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 % change

Ronas Voe 114 [117] [112] 101 [137] 131 80 [101] [102] +1.0%**

Hillswick Ness [238] [233] 266 [286] [293] [249*] [284] [260] [276] [206*] -25.4%

Mu Ness-Wats Ness [261] [273] 292 [336] [264*] [351] [285*] [286] [287] +0.3%

West Burra [230] 204 233 270 [258] [279] 244 [228] [240] +5.3%

West Total 843 827 903 993 902* 994 890* 835 -6.2%**

East Coast 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 % change

Lunning 57 63 [64] [67] 72 84 [68] [88] [64] [74] +15.6%

Levaneap 241 [224] [271] 268 270 [271] 246 [218] [194] -11.0%

Kirkabister 148 140 [164] [170] 169 181 174 179 [151] [170] +12.6%

Aithsetter 93 99 [95] [100] 112 125 114 116 112 [112] 0%

Mousa [115] [99] 137 [158] [194] 182 [176] [154] [132] -14.3%

Boddam-Virkie 116 117 [121] [120] 136 132 [131] 115 [119] +3.5%

East Total 770 755 887 935 978 935 814 801 -12.9 %

Overall Total 1613 1582 1880 1880* 1929 1636

27

Despite a slight to moderate westerly swell at Mu Ness to Wats Ness on 19th April, most birds were already

displaying on the sea outside the foam lines (<10% flushed), the count was considered ‘good’, and in

conjunction with that in 2014 would suggest a decrease of c.18% since 2012. Again, despite a moderate to heavy west that had built overnight, at West Burra on 4th April most birds were already displaying on the sea,

the remainder flushed easily, many recounts were made of particular groups, and the total count was

considered ‘good’, but 14% lower than that in 2012.

Figure 2.2. Counts of adult Black Guillemots at Mu Ness to Wats Ness, west Mainland (black) and West

Burra, southwest Shetland (blue), 1983-2015. Open symbols indicate the lower count when two were made in a year. Black symbols overlap in 2008, blue symbols in 1999, 2007, 2008 and 2009.

In northeast Mainland, many cliff perches along the Lunning coast cannot be seen safely from the cliff top,

but none were flushed on 8th April, when all birds were in displaying groups just offshore; recent small

fluctuations in counts here probably reflect the difficulty of ensuring all birds are seen. Immediately to the

south of this, the longer stretch of coast at Levaneap is more easily counted and most birds were also already displaying on the sea on 13th April; after a series of consistent counts in 2009-12, numbers have declined since

(by 28% since 2012) for no obvious reason, although several large rock falls may have altered nesting habitat

in some geos. Few were also ashore at Kirkabister on 3rd April, where the count was 13% higher than in 2014.

Figure 2.3. Counts of adult Black Guillemots in northeast Mainland, at Levaneap (black), Kirkabister (blue), and Lunning (red), 1982-2015. Open symbols indicate the lower count when two were made in a year. Black

symbols overlap in 2004 and 2013, blue symbols in 1992, 1997, 2010 and 2013, red symbols in 2000 and

2010.

100

150

200

250

300

350

400

1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014

0

50

100

150

200

250

300

350

1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014

28

In southeast Mainland, birds flushed easily on 27th March at Aithsetter, where numbers have been rather

stable since 2010. The few birds ashore also flushed easily along the coast between Boddam and Virkie on

8th April, where numbers and their distribution were very similar to the higher of the two counts in 2014. Although a few birds were impossible to flush on Mousa on 16th April, numbers have undoubtedly declined

since the recent peak in 2010 and the breeding population on the island is currently well under half that of the

late 1980s, when there were peak counts of 347 and 323 on the 22nd April and 7th May 1987, respectively.

Figure 2.4. Counts of adult Black Guillemots in southeast Shetland, at Mousa (black), Boddam to Virkie

(blue) and Aithsetter (red), 1982-2015. Open symbols indicate the lower count when two were made in a year. Black symbols overlap in 2000 and 2004, blue symbols in 1993, 1997, 2006, 2007 and 2013, red symbols in

1993, 2003 and 2007.

50

100

150

200

250

300

350

1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014

29

3. Breeding Red-throated Divers Gavia stellata in Northmavine

The moorland between Sullom Voe and St Magnus Bay has been surveyed for breeding Red-throated Divers biennially since 1994 (annually in 1981-83 and 1989-93). Up to 2011, two checks were made to establish the

number of breeding pairs but in 2013 and 2015 follow-up visits were made later in summer to confirm the

outcome of breeding attempts. Red-throated Divers make a shallow nest scrape (or several scrapes) at the water’s edge and lay a clutch of one or two eggs, so are capable of fledging up to two chicks in a season.

In 2015, all 71 loch and pools in the study area were checked on 2nd–11th June, when 18 breeding pairs were

confirmed, and again on 1st–13th July when a further four breeding pairs were detected, and it was found that six of the earlier breeding attempts had failed. Follow-up checks on the remaining breeding pairs were made

on 27th July, again on 12th-16th August, and finally to the last pair with a chick on 27th August. The number of

lochs with breeding activity (i.e. at least a nest scrape found) was the same as in 2013 but four fewer pairs were confirmed as breeding. There was no evidence of hatching at 13 lochs where incubation had been

confirmed, and six broods of one chick and three broods of two were recorded during July. Two of the single

brood chicks disappeared before they could have fledged, with no evidence of predation, giving moderate

breeding success of 0.45 fledged per laying pair. Of the eight lochs where empty nest scrapes were the only evidence of a breeding attempt, only one loch had been used as a regular breeding site since 2001. Since no

additional nesting activity was detected during the third and fourth checks in 2015, the number of lochs with

diver activity is directly comparable with data from years when only two checks were made (Figure 3.1). This suggests breeding numbers may currently be higher than in the 1990s and 2000s, when empty scrapes were

found or breeding was confirmed at an average of 15 lochs in the 12 years when surveys were made.

Table 3.1. Red-throated Diver nesting activity and breeding success in the Northmavine study area in 2013

and 2015.

Figure 3.1. Red-throated Diver nesting activity in the Northmavine study area, 1981–2015.

0

5

10

15

20

25

30

35

40

45

50

Nu

mb

er

of

loch

s

Adults only

Empty scrape

Breeding proved

Northmavine study area 2013 2015

Lochs with adults present only 11 14

Lochs with empty nest scrapes only 4 8

Confirmed breeding pairs 26 22

Broods known to have hatched 15 9

Broods assumed to have fledged 8 7

Chicks assumed to have fledged 10 10

Mean brood size at fledging 1.25 1.43

Breeding success 0.38 0.45

30

4. Shetland-wide census of moulting Common Eiders Somateria mollissima

The most accurate method of assessing the size of Shetland’s Eider population is to census moulting flocks during August, when adults and immatures are flightless for several weeks, and most juveniles are well-grown

and likely to survive to immaturity. During the 1970s, 1980s and 1990s, moulting flocks occurred at traditional

sites, mainly remote from human disturbance, where birds could feed, rest ashore and find shelter in varying wind directions. These sites were usually at offshore skerries or around particular headlands, and the location

of flocks was predictable although numbers using any particular site varied from year to year. Since the early

2000s, an increasing proportion of the population has spent the late summer at aquaculture sites in sheltered

voes and sounds throughout the islands, and in 2009 and 2012 every salmon farm (active and fallow) and set of mussel lines was checked, as well all the ‘traditional’ sites. Salmon farms need to be checked because Eiders

feed on mussels growing on the infrastructure, as well as using them for shelter, and the concentration of

aquaculture in many areas is such that salmon cages and mussel lines are often within easy swimming distance of each other for flightless Eiders.

The 2015 census began on 1st August, and despite being interrupted by spells of strong winds, was completed

on 31st August. Counts were made from land, and by sea from the SOTEAG RIB, chartered boats, and pollution response and mussel farming workboats, as appropriate for the area and the anticipated size of flocks. As well

as dedicated surveys, a special watch was kept for Eiders while conducting other fieldwork during August.

Results are given clockwise around Shetland, starting in southwest Mainland (Table 4.1).

The coast between Spiggie and St Ninian’s Isle was surveyed from land on 12th August, including Hich Holm

at which males formerly moulted. Only 18 females and juveniles were found, most in the ‘nursery site’ in Bigton Wick. The coast from South Havra, north around Burra, Trondra and the Scalloway and Weisdale Voe

islands, and west to Reawick was surveyed by chartered boat on 17th August. There were 1,071 birds in Clift

Sound, all associated with aquaculture sites, including a single flock that was estimated at 800-860 (80%

males). Apart from five birds at fallow salmon cages in Scalloway Harbour, a flock of 101 males and four females at the traditional site of Burland Skerry completed the total of 1,181 for Burra and Trondra. All 727

birds among the Scalloway Islands were at aquaculture sites, the largest flocks all being at salmon cages: 230-

270 (80% males) off the Score Holms, 200-240 (all males) west of Burwick Holm, and 160-180 (95% males) north of Papa. In Weisdale Voe there were 28 females at mussel lines off Haggersta.

In the west Mainland, Sandsound Voe, The Firth (Tresta), Garderhouse Voe, Skelda Voe, the Gruting Voe area, and Vaila Sound were all surveyed from land on 5th August. All 101 birds found were around mussel

lines, mostly (77) in Vaila Sound; all were females and juveniles and it seemed that mussel lines were being

used as nursery areas. Skelda Ness and the Sil Wick area were not surveyed, but this coast has not been used

by moulting Eiders for many years. Sheila and Penny Gear (Foula Ranger Service) surveyed the east coast of Foula from land on 25th July, finding 33 males, 52 females and 21 chicks/juveniles; the disparity in the sex

ratio would suggest some breeding males had left the island to moult elsewhere.

The Ve Skerries, Papa Stour and the Mainland coast from Melby east to Aith Voe were all surveyed by

chartered boat on 1st August. The count of 47 males and eight females at Ve Skerries was considered accurate

(this site is very exposed to swell and can be problematic to count), none were seen around Papa Stour, and

despite extensive aquaculture in the sheltered voes and sounds east from Brindister to Aith, only eight females and seven juveniles were found there. This survey was followed up by coverage of Olna Firth and Busta Voe

from land on 2nd August. All 379 birds found were at or close to mussel lines, the largest flock being c.280

(80% females) in outer Olna Firth. The east and north coasts of St Magnus Bay were surveyed from land on 12th August, the only birds seen being seven females/juveniles in outer Ura Firth. Inner Ronas Voe was also

checked that day, and again on 22nd August (no birds were seen) when outer Ronas Voe (39 at salmon cages,

including two males), the stacks of Muckle Ossa (five males), and the Ronas Hill coast north to Uyea (seven males at Gruna Stack) were surveyed by chartered boat.

Sullom Voe and Muckle and Little Holms in northern Yell Sound were surveyed from a BP Pollution Response

workboat on 27th August; there were 110 males and 50 females/juveniles in northern Sullom Voe, and eight females/juveniles at Little Holm. Aquaculture sites in southern Yell Sound were checked from land on 5th

August, with 167 birds (including 33 males) near mussel lines in Dales Voe, and 73 (60 males) at salmon

cages in Colla Firth.

31

Table 4.1. Counts of Common Eiders (including juveniles) during August, clockwise around Shetland, 2001-

2015. * = no coverage. Counts in brackets = incomplete coverage compared to other years. Difference is

between numbers in 2012 and 2015; ± > 50 birds in bold.

Area 2001 2002 2005 2006 2009 2012 2015 Diff.

Fitful – South Havra 41 [54] [12] 42 11 20 18 -2

Burra / Trondra 685 341 654 978 1366 635 1181 +546

Scalloway Islands 193 663 573 203 389 305 727 +422

Weisdale Voe 27 4 9 299 667 578 24 -554

Reawick / Seli Voe 40 122 28 16 2 0 0 0

West-side voes * * 205 196 230 102 101 -1

Foula 283 307 231 165 252 239 106 -133

Papa Stour 65 111 24 36 5 0 0 0

Ve Skerries 223 319 271 115 182 115 55 -60

Melby - Aith * * * 101 36 22 15 -7

Olna Firth / Busta Voe 38 110 72 90 241 489 379 -110

E & N St Magnus Bay 57 63 34 9 29 19 7 -12

Muckle Ossa 71 140 170 100 80 7 5 -2

Ronas Voe - Uyea 319 100 36 106 30 50 46 -4

Gloup Holm, Yell 0 * * 3 0 0 * *

NW Unst 104 29 * 8 18 11 [0] [-11]

NE Unst 12 39 [18] 30 24 48 17 -31

S Unst & E Yell * * * 188 151 167 235 +68

Fetlar 0 0 0 0 0 18 0 -18

Sullom Voe 4 22 11 0 4 72 160 +88

North Yell Sound 2 * * 0 3 12 8 -4

South Yell Sound * * 190 109 666 499 240 -259

Out Skerries 246 455 282 372 110 322 60 -262

Whalsay area 4 36 2 22 0 5 6 +1

S Nesting skerries 169 145 76 129 0 35 3 -32

Vidlin/Dury Voes * * * [24] 61 15 35 +20

Gletness-Dales Voe * * [38] 377 493 259 884 +625

N Bressay & Noss 946 651 925 480 162 80 33 -47

Bressay Sound 371 388 192 332 135 162 27 -135

Mail - Levenwick 195 312 361 255 31 66 16 -50

Virkie - Quendale 1035 831 209 355 122 97 91 -6

Fair Isle 239 376 211 126 282 178 120 -58

Total elsewhere 10 8 4 3 0 0 11 +11

Survey total 5379 5626 4838 5269 5782 4627 4610 -17

In west Yell, mussel lines in Whale Firth were checked from land on 10th and 25th August and no birds were

seen. Gloup Holm, off northwest Yell, was not checked but has not been used by moulting Eiders since the

early 1980s. Off northwest Unst, Muckle Flugga was the main gap in coverage in 2015, but 2001 was the last year that substantial numbers of birds were found there (Table 4.1). In northeast Unst, the former moult sites

of Holm of Skaw and Lamba Ness, and aquaculture sites in Balta Sound were checked from land on 31st

August; nine in Wick of Skaw and eight at mussel lines in Balta Sound (all females and juveniles) were the only birds seen. Aquaculture sites off south Unst, east Yell and around Hascosay were surveyed from a mussel

farm workboat on 25th August. Apart from eight females/juveniles at fallow salmon cages off Uyea, the only

birds seen was a flock of c.215 at mussel lines in Basta Voe, Yell. This had been counted more accurately on 10th August (223, including five males), when all other aquaculture sites around Yell were checked from land;

the only other birds seen were two females and two juveniles in Mid Yell Voe.

There is no aquaculture around Fetlar, and the only former traditional moulting site, at Strandburgh Ness, was checked by RSPB staff on 10th August when nothing was seen. The Out Skerries, islands and skerries around

Whalsay, skerries off South Nesting Bay, and aquaculture sites in Vidlin Voe were all surveyed from the

32

SOTEAG RIB on 13th August; a scatter of birds totaled 77 (including 11 males), mainly around Out Skerries.

Aquaculture sites in Dury Voe were checked from land on 8th August, and 27 birds (including 14 males) were

found at two separate salmon farms. The Mainland coast from Eswick in South Nesting (including the Hoo Stack and Sneckan) south to Gulber Wick, and the entire coasts of Bressay and Noss were surveyed from the

SOTEAG RIB on 7th August. A large flock found at salmon cages in outer Cat Firth was counted from land

early the following morning (672 males, 106 females), while the other main flocks were 19 (including 3 males) at salmon cages in the South Voe of Gletness, 48 (46 males) at salmon cages in Lax Firth, 21 females and

juveniles at mussel lines in Dales Voe, 25 (10 males) at the Brethren rocks east of Kebister Ness, and 25

females and juveniles in Bressay Sound.

In southeast Mainland, the coast between the Mail Skerries and Levenwick Ness was surveyed from land on

2nd August, while the coast of Mousa was checked from land by RSPB staff on 7th August; a scatter of five

females and 11 juveniles were the only birds seen, with none in the former ‘nursery area’ of inner Sand Wick. The coast from Grutness to Garths Ness was surveyed from land on 8th August, when a moderate south-

westerly swell meant no birds were likely to been on the ‘blind’ sides of Horse Island and Ladies Holm. Of

the 91 birds recorded, 68 (two males, 32 adult females, 34 immatures and juveniles) were in the ‘nursery area’

in the northeast corner of the Bay of Quendale. The entire coast of Fair Isle was surveyed from land by FIBO staff on 28th August, when 51 males, 39 females and 30 juveniles were found.

Given that numbers in some flocks had to be estimated, the close similarity of the 2012 and 2015 survey totals is somewhat spurious, but the 2015 figure does suggest that (a) the 2009-12 decrease of 20% was real and not

due to some large flocks having been overlooked, and (b) there has not been a further substantial decline in

the population since 2012. Again, given the uncertainties of estimating the proportions of adult males in larger flocks, one cannot be too precise about the sex ratio of the population, but counts in winter suggest that adult

males outnumber adult females, perhaps by somewhere between 55:45 and 60:40, and the counts of moulting

birds tends to confirm this (Table 4.2).

The area between southern Clift Sound and Weisdale Voe, including the Scalloway Islands, held 42% (1,932

birds) of the population in 2015 compared to 33% (1,518) in 2012 and 42% (2,422) in 2009, with outer Olna

Firth holding the only other large concentration on the western side of Shetland (8% of the population). In eastern Shetland, the largest concentration was in the Gletness to Dales Voe area (19% of the population),

with smaller flocks in southern Yell Sound (5%), and in Basta Voe (5%). Overall, 82% of the population was

associated with aquaculture sites in August 2015, compared to 64% in August 2012, and away from aquaculture sites the largest gathering was in northern Sullom Voe (3% of the population).

Table 4.2. The 2012 and 2015 Common Eider census figures by recorded sex and age category, for West Shetland (Fitful Head to Muckle Flugga, including Foula) and East Shetland (Skaw, Unst to Bay of Quendale,

including Yell Sound and Sullom Voe, and Fair Isle). Undetermined ‘brown’ birds comprised an unknown

ratio of adult females, immatures and fully-grown juveniles. The percentage of the total that was at or close to salmon cages and mussel lines is given.

Adult

males

Adult

females

Undetermined

‘brown’ birds

Juveniles Total % at

aquaculture

W. Shetland 2012 1511 58.3%

426 16.4%

540 20.8%

115 4.4%

2592 77.0%

W. Shetland 2015 1604 60.1%

767 28.7%

230 8.6%

69 2.6%

2670 89.1%

E. Shetland 2012 946

46.5%

431 21.2%

566 27.8%

92 4.5%

2035 48.0%

E. Shetland 2015 1019 52.5%

598 30.8%

225 11.6%

98 5.1%

1940 72.5%

Total 2012 2457

53.1%

857 18.5%

1106 23.9%

207 4.5%

4627 64.3%

Total 2015 2623 56.9%

1365 29.6%

455 9.9%

167 3.6%

4610 82.1%

33

5. Winter counts of seaduck and diving seabirds

5.1. Sullom Voe and Yell Sound

A survey on 19th January (two observers) was hampered slightly by slow-moving light showers during the

section in Yell Sound from Linga north past Samphrey and Bigga and into Orka Voe, but conditions in Sullom Voe and for the afternoon section in Yell Sound then improved to near perfect with no wind and thin, high

cloud. A second survey on 13th December (two observers) was also hampered at times by slow-moving, nearby

showers which freshened the breeze to a F3 for short periods, but this was not thought to have affected counts

along most of the route.

Sullom Voe is of national importance for wintering numbers of Red-breasted Mergansers and Slavonian

Grebes but both species react to the survey boat and can be difficult to count accurately. Red-breasted Mergansers were particularly flighty on both surveys and the totals for Sullom Voe were probably slightly

conservative as we tried to avoid double-counting birds flying ahead of the boat. It is easier to keep track of

the smaller number of Slavonian Grebes and the totals were probably accurate (Table 5.1); both species utilise

the entire coastline fringes of Sullom Voe but avoid the deeper waters of the central voe. Only three Great

Northern Divers were seen in Sullom Voe in January and two in December, all in the northern half of the

voe.

Table 5.1. Counts of seaduck and diving seabirds in Sullom Voe during winter.

Winter 2009/10 2010/11 2011/12 2012/13 2013/14 2014/15 2015/16

Date 10/12 12/2 21/12 16/1 23/1 10/1 19/1 13/12

Common Eider 0 2 0 2 0 0 3 11

Long-tailed Duck 0 0 0 1 1 2 2 0

Common Scoter 0 0 0 0 0 1 0 0

Velvet Scoter 0 0 1 0 0 0 1 0

Goldeneye 3 49 39 33 47 18 30 19

Red-breasted Merganser 131 121 194 74 124 141 141 112

Goosander 0 0 0 0 1 0 1 0

Red-throated Diver 4 0 0 1 2 1 0 4

Black-throated Diver 0 0 0 0 1 0 0 1

Great Northern Diver 2 1 5 2 3 8 3 2

Slavonian Grebe 25 31 18 29 21 32 26 16

Cormorant 27 7 62 5 18 8 2 0

Shag 420 119 732 87 90 158 125 141

Common Guillemot 0 0 0 1 0 2 0 0

Razorbill 0 0 0 1 2 1 0 0

Black Guillemot 68 49 145 121 195 156 143 85

Little Auk 0 0 0 1 0 0 1 2

Puffin 0 0 0 0 0 1 0 0

Total 680 379 1208 358 505 529 478 393

In Yell Sound (Table 5.2), the main groups of Common Eider in January were in southern Linga Sound (47)

and around Tinga and Sligga Skerries (31), but fewer were present in December. Although Long-tailed Ducks were present at each of their favoured feeding areas in January, numbers were low compared to the late 1990s

(200-300), with only 20 over the shallows west of Lunna Ness and 32 west of Orfasay. The December count

was the lowest in the past 30 years, and while cryptically-plumaged, the distribution of this species in Yell Sound is very predictable and it is unlikely many were overlooked in any moderate conditions. Great

Northern Divers remain very scarce in Yell Sound, with two seen in January and four in December. Large

roosts of Cormorants and Shags were found on both surveys and, as is usually the case, many (especially Cormorants) flew off as the boat passed (even at a range of 300 m); while we try not to double-count these

birds, for both species the January totals were probably only accurate to ± 50, while the December totals may

have been too high by 100-150 birds. As in recent years, the scarcity of Common Guillemots and Razorbills

in Yell Sound in mid-winter (on both surveys) was noteworthy.

34

Since the first survey of the Yell Sound route in 1976/77, the nature of the boats used as viewing platforms

has improved immeasurably, from the wooden Consort in the 1970s and early 1980s on which two observers braced themselves standing beside the wheelhouse barely a metre above sea-level, to the Dunter III from

2003/04 on which two observers (often three) are seated in swivel chairs on a bridge 5 metres above sea-level.

The quality of binoculars has also improved, allowing birds to be detected at a greater distance, as has weather forecasting, meaning fewer surveys have been conducted in moderate conditions. Despite all this, only single

figures of Great Northern Divers have been recorded on these surveys since winter 1989/90, when 12 were

seen off the west coast of Lunna Ness on 28th November (Figure 5.1). This compares to the 44 recorded on

28th November 1978 (with a further nine in Sullom Voe), the last such survey before the 31st December 1978 Esso Bernicia oil spill, following which 131 oiled Great Northern Divers were found the shores of Yell Sound

and Sullom Voe in early 1979. Recent studies in North America have confirmed that adult Great Northern

Divers show winter site fidelity, something that has long been suspected for those wintering in Shetland. Even allowing for this, it is remarkable that this former wintering stronghold has not yet been repopulated so long

after a major mortality incident.

Table 5.2. Counts of seaduck and diving seabirds around the southern Yell Sound islands during winter.

Count conditions: ** = moderate to good, *** = good or excellent throughout.

Figure 5.1. Counts of Great Northern Divers during winter (late November to early March) from boats along the standard survey route in southern Yell Sound. Plotted are the higher of 1-3 counts per winter until 1998/99,

and of 1-2 counts per winter from 1999/2000; no surveys were made in 1994/95 or 1995/96.

0

10

20

30

40

50

Great Northern Diver: Yell Sound

Pre-Bernicia good conditions

Post-Bernicia good conditions

Post-Bernicia moderate conditions

Winter 2009/10 2010/11 2011/12 2012/13 2013/14 2014/15 2015/16

Date 10/12 12/2 21/12 16/1 23/1 10/1 19/1 13/12

Count conditions *** *** ** *** *** *** ** **

Common Eider 12 70 19 55 27 57 83 21

Long-tailed Duck 105 47 46 80 98 73 82 23


Goldeneye 1 6 28 18 8 6 6 2




Slavonian Grebe 0 0 5 3 6 4 1 0

Cormorant 322 361 484 104 353 230 463 579

Shag 1444 1038 575 513 691 440 706 911


Razorbill 1 0 1 0 0 1 0 0

Black Guillemot 602 281 362 325 580 513 349 286

Little Auk 5 0 0 1 0 0 0 5

Puffin 0 0 0 0 4 0 1 0

Total 2517 1815 1528 1121 1786 1344 1706 1839

35

5.2. Rova Head to Kirkabister, East Mainland

A survey on 12th December (two observers) was in generally excellent conditions, although light levels were rather low on the first (Rova Head to Dales Voe) and last sections (West Voe of Skellister to Kirkabister). The

only concentrations of Common Eiders were at salmon cages in Lax Firth (26) and near mussel lines in inner

Cat Firth (74), while Long-tailed Ducks were mainly found in their favoured haunts of outer Dales Voe and Lax Firth (73), and between Glet Ness and the Aswick Skerries (31). The Red-breasted Merganser total was

unexceptional for the area, although this remains the most important coast for the species on the east coast of

Shetland. The count of Red-throated Divers may have been too high, as a group of five that flew north past

the boat off Eswick lighthouse may have been the same as seen later off Kirkabister. The total of 110 Great

Northern Divers was similar to those on four of the five most recent surveys, with 70 of the birds recorded

between Gletness and Kirkabister; the low count in January 2011 may have been due to a freshening breeze

during the latter half of the survey reducing the long-range detectability of this cryptic species. Slavonian

Grebes were present in the usual locations, there was no particular reason why any might have been

overlooked, and the apparent decrease in wintering numbers since 2011/12 seems to mirror that in Sullom Voe

(Table 5.1). The totals of Shags and Black Guillemots were unexceptional, while the small number of pelagic

auks seen (Common Guillemot, Razorbill, Little Auk, Puffin) all appeared healthy.

Table 5.3. Counts of seaduck and diving seabirds along the coast from Rova Head (north Bressay Sound) to Kirkabister (North Nesting) during winter. Count conditions: *** = good to excellent throughout.

Winter 2007/08 2008/09 2009/10 2010/11 2011/12 2012/13 2013/14 2015/16

Date 10/2 9/2 11/12 27/1 19/12 30/11 17/2 12/12

Count Conditions *** *** *** *** *** *** *** ***

Common Eider 136 163 204 125 126 93 59 154

Long-tailed Duck 119 125 164 98 119 134 161 121



Goldeneye 30 39 37 46 31 27 16 9


Goosander 0 6 1 0 0 0 0 0



White-billed Diver 0 1 0 0 0 0 0 0

Slavonian Grebe 42 43 49 61 57 48 46 38

Cormorant 10 98 5 115 69 41 52 11

Shag 436 543 507 327 515 382 419 362


Razorbill 16 1 0 0 3 4 7 5

Black Guillemot 362 433 603 336 422 409 281 329

Little Auk 1 0 2 0 0 0 0 8

Puffin 3 0 0 0 4 0 1 1

Total 1394 1764 1817 1288 1665 1415 1332 1280

36

5.3. Whiteness Voe to Skelda Voe, West Mainland

This area was counted from land by Paul Harvey and Rory Tallack (Shetland Amenity Trust) on the morning of 5th February; conditions were calm initially but a breeze freshened to SW 3 by the finish at 12.30pm (Table

5.3). The main concentration of Common Eiders (88) was in The Firth, Tresta, where there are extensive

mussel farms, while the total of 20 Long-tailed Ducks was the lowest recorded for the area (Figure 5.2). The total of 109 Red-breasted Mergansers was also unexceptional, the main concentration (37) being in

Whiteness Voe. The 25 Great Northern Divers seen was also a rather low count. The area holds one of the

largest concentrations of Slavonian Grebes in the UK, and the total of 66 recorded (24 in Whiteness Voe,

singles in Stromness and Sandsound Voes, 13 in Weisdale Voe, 12 in The Firth, five in Sand Voe, ten in Seli Voe) was only slightly lower than the counts in winters 2009/10 to 2011/12.

Table 5.4. Counts from land of diving seabirds and seaduck in the voes between Whiteness Voe and Skelda

Voe. Count conditions were good to excellent throughout on each date.

Winter 2006/07 2007/08 2009/10 2010/11 2011/12 2012/13 2013/14 2014/15

Date 7/2 19/2 12/2 25/1 23/1 13/12 7/2 15/2

Common Eider 179 178 201 169 58 317 42 134

Long-tailed Duck 38 47 46 33 36 26 23 20



Goldeneye 20 16 35 11 21 18 28 15


Goosander 0 0 2 1 3 0 1 0

Smew 0 0 1 0 0 0 0 0


Black-throated Diver 0 0 0 0 0 0 1 0


Slavonian Grebe 67 68 77 73 74 55 57 66

Cormorant 9 35 26 14 10 17 27 8

Shag 73 127 101 103 104 145 127 128


Razorbill 3 9 0 1 0 3 11 4

Black Guillemot 64 108 57 76 76 44 106 81

Puffin 0 0 0 0 0 0 1 1

Total 605 824 727 587 528 800 735 592

Figure 5.2. Counts from land of Long-tailed Duck in the voes between Whiteness Voe and Skelda Voe.

Conditions were good to excellent on each survey.

0

25

50

75

100

125

150

Long-tailed Duck

37


Monthly beached bird surveys are carried out by the authors and a team of long-term volunteers. Coverage includes Unst, north and east Yell, south Fetlar, west Bressay, Fair Isle, 49 beaches on the east and west coasts

of Mainland, mainly on the ‘outer’ coasts, as well as 15.6 km of the northern half of Sullom Voe, and nine

other beaches (totaling 5.2 km) in Yell Sound. Any monthly variation in coverage is largely due to beaches with nesting terns not being surveyed in May, June and July. All bird corpses found (down to single wings

with all the primary feathers present) are checked for oil contamination and rings, aged as far as possible, and

removed from the beach. Results presented are for seabird and seaduck species only.

6.1. Incidence of oiling in 2015

All 27 seabirds found oiled were on the west coast of Shetland, mostly (21) in northwest Mainland between Mavis Grind and Ronas Voe, and mostly (19) between March and July (Tables 6.1, 6.3). Species oiled were

Fulmar (22), Gannet (2), Herring Gull (1), Great Black-backed Gull (1) and Kittiwake (1); only the Great

Black-backed Gull and two Fulmars were heavily oiled and would have died quickly. No oil was reported on

beaches during the year. Eight samples of oiled plumage were analysed (Table 6.2). All were fuel oil residues of unknown origin, although that from the very heavily oiled (100%) Great Black-backed Gull on St Ninian’s

Ayre on 22nd February had been refined from a Russian crude.

Table 6.1. Summary details for the Shetland Beached Bird Survey. Total figures are from March 1979.

Year Km. Corpses Oiled Total/km % Oiled Oiled/km.

2006 551.50 1,086 17 1.969 1.57 0.031

2007 559.40 1,069 36 1.911 3.37 0.064

2008 577.80 1,159 90 2.006 7.77 0.156

2009 553.90 942 40 1.701 4.25 0.072

2010 551.30 857 46 1.555 5.37 0.083

2011 577.80 935 23 1.618 2.46 0.040

2012 579.20 1031 21 1.780 2.04 0.036

2013 581.12 811 49 1.396 6.04 0.084

2014 587.52 1,152 11 1.961 0.96 0.019

2015 585.17 691 27 1.181 3.91 0.046

TOTAL 21,719.31 70,110 4,733 3.228 6.75 0.218

5-Year Annual Means: 1979-1983 4.064 9.98 0.408

1984-1988 3.933 7.86 0.311

1989-1993 3.990 7.19 0.285

1994-1998 4.307 9.50 0.409

1999-2003 3.171 2.39 0.073

2004-2008 2.163 2.97 0.061

2009-2013 1.610 4.04 0.063

2014-2015 1.571 2.44 0.033

Table 6.3. Results of analyses of oil samples collected in 2015. S = slightly oiled (< 10%); M = moderately

oiled (10-25%); H = heavily oiled (>25%). *There was a probable match between samples 245 and 246.

No. Date Location Sample Type Possible type; source 240 22/1 Sandwick, Eshaness Kittiwake S Fuel Accidental release or illegal bilge discharge

241 21/2 Footabrough, W

Mainland

Gannet S Fuel Accidental release or illegal bilge discharge

242 22/2 St Ninian’s, SW

Mainland

Great Black-

backed Gull H

Fuel Produced from Russian crude; accidental

release or illegal bilge discharge

243 29/3 Braewick, Eshaness Fulmar S Fuel Accidental release or illegal bilge discharge

244 22/4 Tangwick, Eshaness Fulmar S Fuel Accidental release or illegal bilge discharge

245 24/6 Stenness, Eshaness Fulmar H Fuel* Accidental release or illegal bilge discharge

246 27/7 Stenness, Eshaness Fulmar M Fuel* Accidental release or illegal bilge discharge

247 21/10 Meal, West Burra Fulmar S Fuel Accidental release or illegal bilge discharge

38

Table 6.2. Seabirds and seaduck found on beached bird surveys in 2015. For each species the first figure

given each month is the total found, the second the number that were oiled (in bold).

Other species: Whooper Swan (1), Greylag (35), Pink-footed Goose (1), Grey Heron (1), Mallard (3), Teal (1), Oystercatcher (6), Lapwing (1), Curlew (8), Whimbrel (2), Rock Dove (12), Blackbird (1), Starling (1),

Hooded Crow (2), Raven (4).

Net/rope/hook tangled: Fulmar (1: 1 rope), Gannet (10: 2 fish net, 4 monofilament net, 2 fish hook, 2 plastic strapping), Great Black-backed Gull (1: 1 rope), Razorbill (1: 1 rope).

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

Common Eider 0 2 3 2 0 1 0 1 0 0 0 0 9

Red-br. Merganser 0 0 0 0 0 0 1 0 0 0 0 0 1

Red-throated Diver 0 0 0 0 0 1 0 1 0 0 0 1 3

Fulmar 11 12 27/3 26/3 51/2 48/10 54/3 46 39 13/1 8 5 340/22

Gannet 3/1 3/1 5 10 10 6 8 3 5 5 3 7 68/2

Cormorant 0 0 2 0 1 0 0 0 0 0 2 0 5

Shag 0 0 1 1 4 2 5 2 1 0 1 1 18

Arctic Skua 0 0 0 0 0 1 0 0 0 0 0 0 1

Great Skua 0 0 0 0 2 2 0 4 1 0 0 0 9

Common Gull 0 0 0 2 5 3 4 3 2 0 1 1 21

Lesser Bl.-backed Gull 0 0 0 1 2 0 0 0 0 0 0 0 3

Herring Gull 4 2 2 0 5 5/1 9 10 6 7 0 8 58/1

Iceland Gull 0 1 1 0 1 0 0 0 0 0 0 0 3

Glaucous Gull 2 0 0 0 0 0 0 0 0 0 0 0 2

Great Bl.-back. Gull 6 5/1 4 5 9 3 4 5 1 4 0 0 46/1

Kittiwake 2/1 4 2 1 0 3 2 5 1 0 4 4 28/1

Arctic Tern 0 0 0 0 0 0 3 0 0 0 0 3 3

Common Guillemot 1 1 2 5 6 7 8 3 6 1 3 0 43

Razorbill 0 0 0 0 0 2 3 0 0 0 0 0 5

Black Guillemot 1 1 0 0 5 0 1 1 1 0 0 1 11

Little Auk 0 0 0 0 0 0 0 0 0 0 1 1 2

Puffin 3 1 1 1 1 1 1 1 1 0 0 0 11

Total 33 32 50 54 102 86 103 85 64 30 23 29 691

Oiled 2 2 3 3 2 11 3 0 0 1 0 0 27

Km. surveyed 49.5 49.5 49.6 49.6 49.6 48.0 48.2 49.6 49.6 48.1 44.8 49.5 585.17

Corpses / km. 0.67 0.65 1.01 1.09 2.06 1.79 2.14 1.72 1.29 0.63 0.51 0.59 1.18

% oiled 6.1 6.3 6.0 5.6 2.0 12.8 2.9 0 0 3.3 0 0 3.9

Oiled / km. 0.04 0.04 0.06 0.06 0.04 0.23 0.06 0 0 0.02 0 0 0.05

Oiled after death 0 0 0 0 0 0 1 0 0 0 0 0 1

Net/rope/hook tangled 0 2 1 5 1 1 2 1 0 0 0 0 13

Other species 1 2 2 4 7 9 12 19 12 1 8 2 79

39

6.2. Non-oiled mortality

In contrast to 2014, very few pelagic auks were found in the first three months of the year: four Guillemots (one first-winter, three older), no Razorbills, and five Puffins (one first-winter, two adults, two unaged)

(Figure 6.1, Table 6.4). Guillemots were attending the Sumburgh Head colony in strength periodically from

the beginning of the year, often from dawn until dusk and often on days of strong winds, so the scarcity of corpses on beaches suggested they were not feeding close to Shetland.

Only five first-winter Guillemots were found on the September and October surveys (Table 6.4), and the other

auk species were also notable by their absence on the early winter surveys.

Figure 6.1. The number of Guillemots (upper, per km), Razorbills (middle, per 10 km) and Puffins (lower, per 10 km) recorded on monthly beached bird surveys, January 2006 to December 2015.

0.0

0.5

1.0

1.5

2.0

2.5

Guillemot oiled

Guillemot clean

0.0

1.0

2.0

3.0

4.0

5.0

6.0

Razorbill oiled x10

Razorbill clean x10

0.0

1.0

2.0

3.0

4.0

Puffin oiled x10

Puffin clean x10

40

Table 6.4. Age composition of Common Guillemots found on the 2015 beached bird surveys. No white tips

to the greater underwing coverts means birds were older than their first year, white tips means they were in

their first winter year. Percentages given are of the total of aged corpses only.

Month January February March April May June

Guillemot No. % No. % No. % No. % No. % No. %

No white tips 0 0 1 100 2 100 4 80 5 83 7 100

White tips 1 100 0 0 0 0 1 20 1 17 0 0

Unaged 0 0 0 0 0 0

Total 1 1 2 5 6 7

Month July August September October November December

Guillemot No. % No. % No. % No. % No. % No. %

No white tips 8 100 3 100 2 33 0 0 1 33 0

White tips 0 0 0 0 4 67 1 100 2 67 0

Unaged 0 0 0 0 0 0

Total 8 3 6 1 3 0

Late winter is normally the period of peak mortality for Shags, but this varies considerably from year to year.

Despite very windy weather in January, none were found dead on the January or February surveys, and only single immatures on the March and April surveys, the lowest incidence at that time of year in the past 36 years

(Figure 6.2). Population decline may have contributed to this (as suggested by Figure 6.3), but the scarcity

of corpses on beaches would suggest relatively high survival for that time of year in 2015.

Figure 6.2. The number of Shags found per 10 km on the January to April beached bird surveys, 1980-2015.

Figure 6.3. The annual number of Shags found per km on beached bird surveys in Shetland, 1979-2015.

0

1

2

3

4

5

6

Unaged

Immature

Adult

0.0

0.1

0.1

0.2

0.2

0.3

0.3

0.4

Oiled

Clean

41

7. Publications

Camphuysen, K. & Heubeck, M. 2016. Beached bird surveys in the North Sea as an instrument to measure chronic oil pollution. In: Carpenter, A. (ed.) Oil Pollution in the North Sea: 193-208. Springer,

Heidelberg/New York.

Harris, M. P., Heubeck, M., Newell, M. A. & Wanless, S. 2015. The need for year-specific correction factors (k values) when converting counts of individual Common Guillemots Uria aalge to breeding pairs. Bird

Study 62: 276-279.

Heubeck, M., Mellor, R. M., Gear, S. & Miles, W. S. T. 2015. Population and breeding dynamics of European

Shags Phalacrocorax aristotelis at three major colonies in Shetland, 2001-2015. Seabird 28: 55-77.

8. Acknowledgements

Paul Harvey assisted with winter seabird surveys; thanks also to boatman Jonathan Wills. Roger Riddington

helped with boat surveys during June. The August Eider census was greatly assisted by boatmen Jim Dickson,

Martin Pottinger, Christopher Thomason and George Lamont Williamson, and for counts from land by Newton Harper and Malcolm Smith. The following participated in the beached bird survey during 2015: Richard

Ashbee, Gary Bell, Robbie Brookes, Juan Brown, Alastair Christie-Johnston, Andy Cook, Martha Devine,

Harry Edwards, Dick Foyster, Andy Gear, Paul Goddard, Newton Harper, Phil Harris, Derick Herning, Sally Huband, Tommy Hyndman, Logan Johnson, Micky Maher, Helen Moncrieff, Rebecca Nason, Dave Okill,

David Parnaby, Mike Pennington, Roger Riddington, Alan Slater, Malcolm Smith, Jonathan Swale, Brydon

Thomason, Howard Towll and Glen Tyler.

The Ornithological Monitoring Programme is funded by the Sullom Voe Association Limited.

42

Appendix 1. Seabird monitoring on Foula in 2015, conducted by Sheila Gear (Foula Ranger Service).

Common Eider. Eiders numbers were well down on the annual late July count, after being low throughout the winter. Their breeding season was late and success was poor. The first chicks were seen on 22nd June.

Conditions on 25th July were good with a light NNE wind, cloudy but bright, clearing to sunny.

22/7/06 27/7/07 26/7/08 27/7/09 24/7/10 26/7/11 27/7/12 25/7/13 27/7/14 25/7/15

Males 82 73 94 110 48 74 108 94 81 33

Females 61 60 70 89 66 51 50 71 87 52

Adults 143 133 164 199 114 125 158 165 168 85

Chicks 37 27 25 53* 19 26 81 27 49 21

Total 180 160 189 252 133 151 239 192 217 106

Brood/1 7 11 8 10 8 7 7 15 5 3

Brood/2 8 4 7 12 3 6 12 3 11 2

Brood/3 2 1 1 4 0 1 8 2 6 2

Brood/4 2 0 0 1 0 1 4 0 1 2

Brood/5 0 1 0 0 1 0 2 0 0 0

Mean Br. 1.95 1.59 1.56 1.85 1.58 1.73 2.45 1.35 2.13 2.33

Red-throated Diver. Divers had a relatively successful season again, although not as good as in 2014. Eight

sites were also occupied by Greylags, and much aggressive fighting was observed between the two species. Site D held the only pair to fledge two chicks, one of which was leucistic, similar to the chick at this site in

2014. Eleven chicks were initially assumed to have fledged, but one was later found dead away from its loch

with a deformed wing and was probably incapable of sustained or actual flight.

Foula Red-throated Divers 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Sites occupied at least once 13 11 10 12 10 13 12 13 13 12

Breeding attempts 9 7 8 11 9 11 8 12 12 12

Sites where chicks hatched 7 6 6 7 5 7 6 7 11 11

Minimum number of chicks 9 7 6 10 5 9 8 9 17 12

Chicks presumed fledged 3 7 4 9 4 5 5 4 15 10

Breeding success 0.33 1.00 0.50 0.82 0.44 0.45 0.63 0.33 1.25 0.83

Northern Fulmar. Four of the monitoring sites were picked at random, AOS were scored on 28th May, 31st May and 3rd June, and chicks were counted on 21st August. Fulmars had a poor year with the wetter areas of

cliff producing no fledglings. Some fledglings were dirty and bedraggled. Using birds present on possible nest

sites on all three observations at the end of May and beginning of June as the criteria for AONs, productivity was 0.26 fledglings per AON (33 fledglings). However, as in 2014 a third (16) of the total number of fledglings

were at (‘extra’) sites scored as AOS on fewer than three early checks.

Plot Total

AOS

AOS on all 3

checks (%)

Chicks at all-3-check sites

+ ‘extra’ sites

Success

1. Voe 94 28 (29.8%) 3 + 4 7/32 = 0.22

2. Brae Daek End 52 29 (55.8%) 8 + 3 11/32 = 0.34

4. W. Inner Sellapiddle 68 38 (55.9%) 7 + 2 9/40 = 0.23

7. Shobul 62 28 (45.2%) 11 + 7 18/35 = 0.51

Total 276 123 (44.6%) 29 + 16 45/139 = 0.32

Mean of 4 plots 0.33

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European Shag. Shag numbers were again very low and many areas remained deserted, including four of the

ten productivity plots, which were all checked on ten dates between 20th April and 25th July. Although

incubation was recorded at a high proportion of sites with nest material, productivity was only moderate at 0.79 fledged per incubating nest, with some chicks found dead and some nests apparently washed away by

rain and by the sea.

Shag 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Trace nests 3 3 3 2 1 0 4 3 0 1

Empty nests 0 1 10 2 1 1 3 4 0 1

Incubating nests 33 24 27 44 41 27 10 4 35 29

% Incubating 91.7 85.7 67.5 91.7 95.3 96.4 58.8 36.4 100 93.5

Young fledged 35 25 7 55 56 20 5 3 66 23

Fledged / inc. 1.06 1.04 0.26 1.25 1.37 0.74 0.50 0.75 1.89 0.79

Arctic Skua. The first bird was seen ashore on 26th April but most birds returned late. Only 12 were counted

on 13th May and most pairs did not lay until June. There were 28 AOT, one of which only had a single bird, and 26 pairs were seen to lay with a mean clutch size of 1.62. Seventeen chicks were ringed and all survived

to fledge (one apparently weak chick was not ringed, and later found dead). Most pairs lost one chick around

hatching but four pairs fledged two chicks each. Productivity was 0.67 fledglings per pair (0.61 per AOT). No predation of fledglings by Great Skuas was observed.

Arctic Skua 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

First seen 26/4 26/4 21/4 24/4 26/4 22/4 3/5 29/4 26/4

AOT 79 71 41 63 50 41 37 35 24 28

Pairs laid 61 42 10 49 39 32 27 26 21 26

Mean clutch 1.68 1.69 1.71 1.43 1.73 1.63 1.58 1.77 1.70 1.62

Fledged 2 0 0 22 (1) 0 4 0 18 17

Success/AOT 0.03 0 0 0.35 0.00 0 0.11 0 0.75 0.61

Great Skua. Great Skuas again returned late with the first bird seen on 3rd April; many did not come ashore

until May. The sample plot in the Bitten was monitored. Three visits of several days each are usually made

to the study area: once most are thought to have laid; to mark/ring chicks (usually 3rd week of July); to assess the number of chicks surviving to fledge. This last can be difficult because predation of chicks can be high in

their last week before fledging, as they hide less and walk around the territory in the open. Details of how

the annual number assumed fledged was derived are therefore given. Predation of chicks was very high in

2015 and only 13 chicks survived to mid July when they were ringed. Predation by adults continued and only three chicks survived to fledge, giving productivity of 0.07 per pair.

Great Skua 2007 2008 2009 2010 2011 2012 2013 2014 2015

First seen 8/4 4/4 10/4 6/4 2/4 28/3 10/4 10/4 3/4

AOT monitored 49 62 45 48 53 38 41 48 42

Mean clutch 1.69 - 1.94 1.87 1.74 1.76 1.54 1.88 1.62

Fledged (*see below) 30 70 65 11 14 8 3 8 3

Success/AOT 0.61 1.13 1.44 0.23 0.26 0.21 0.07 0.17 0.07

*2007: 30 chicks (2 flying) on 9-10/8; predation continued after this count so productivity over-estimated.

*2008: 57 live chicks (marked) and 9 dead on 28/7; most chicks flying on 9/8 but a further 13 live and 4

dead unmarked found, so assume 70 fledged.

*2009: 66 chicks marked on 24-25/7; fledglings not counted but one marked chick found dead 21/8. *2010: 40 chicks ringed on 21 & 26/7; 9 fledged, 2 unfledged and 35 dead on 8/8.

*2011: 38 chicks ringed on 21 & 28/7, 3 of which predated; 11 fledged and 3 unfledged (adults defending

well so assume fledged) on 14/8. *2012: 17 chicks ringed on 24 & 27/7; 8 fledged and 4 unfledged (these assumed didn’t fledge) on 12/8.

*2013: 16 chicks ringed between 21/7 & 8/8; 3 fledglings on 19/8.

*2014: 14 chicks ringed on 21-22/7; 8 fledglings (including one un-ringed) on 12/8. *2015: 13 chicks ringed on 19 & 22/7 (2 of which predated); 3 fledglings on 15/8.

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Common Gull. Only two pairs of Common Gulls nested at the Groups Quarry. Both pairs lost their eggs not

long after laying and did not relay.

Herring Gull. 14 Herring Gulls were present at the Swaa but only 4 pairs nested, along with one pair of Lesser Black–backed Gulls. Only 3 chicks were seen.

Black-legged Kittiwake. The all-island count from the sea was made on 24th June. Empty nests were counted

as well as attended nests because the count was somewhat late in the season. Despite having had a better season in 2014, numbers were well down.

Black-legged Kittiwake 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Census count (AON) 1065 997 - 509 582 480 378 327 361 277

% change per year -6.4 -28.5 +14.3 -17.5 -21.3 -13.5 +10.4 -23.3

At the breeding success subcolony In Under da Stee, a rock fall had occurred high above the site and material

was still coming down, so it was monitored from the sea when possible. Normally, the nests here survive from

the previous season but none had survived from 2014. Only two pairs nested, fledging one chick. Five checks

were made at the Hodden subcolony from 2nd June to 17th August. There were a few more well-built nests than in 2014 but only four chicks were seen, all surviving to fledge.

In under da Stee 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Completed nests 118 91 13 70 52 50 44 32 20 2

Fledged 26 1 0 23 3 0 0 0 0 1

Success 0.22 0.01 0 0.33 0.06 0 0 0 0 0.50

Hodden 2008 2009 2010 2011 2012 2013 2014 2015

Completed nests 2 46 31 22 20 18 18 21

Fledged 0 22 0 2 0 0 15 4

Success 0 0.48 0 0.09 0 0 0.83 0.19

Mean success 0 0.41 0.03 0.05 0 0 0.42 0.35

Arctic Tern. Arctic terns were very late and only returned at the end of May with a few at the Clettins and

20–30 south of the airstrip. On 16th June c.300 terns were on the airstrip and they subsequently laid east of the

Dykes, the first eggs being seen on 22nd June.

A further influx of terns occurred in mid July. On 22nd July, 10 were counted at the Clettins and 683 at the

colony east of the Dykes on 22nd July. By the end of July some of these new birds had laid, mainly only a single egg. Some of the first terns to lay had chicks with feathers but about 40% of the chicks, of various ages,

were lying dead. On 6th August about half the terns had left the island. On 16th August the rest of the terns left

the breeding area and gathered at the Hame Banks with c.30 surviving fledglings.

Throughout the season, terns were seen bringing in very small fish and occasional moths; none were seen with

sandeels. Two Great Skuas were observed killing tern fledglings as they first fluttered off the ground, and

fighting aggressively over them; however they did not appear to have any interest in eating them.

Black Guillemot. Conditions were good on both the pre-breeding counts and numbers almost reached the high of 2012. On the 1st count birds were mainly at sea except at the Sandy Loo Geo where they were all sitting

up. On the 2nd count most birds were ashore and very reluctant to fly off. The first fledglings were seen on 17th

August.

Area counted Date & time Weather & tide Count

East coast 18/4: 6.00–10.00am Wind W 3, no swell, cloudy, tide flowing 179 adults

East coast 20/4: 5.30–7.55am Wind L&V, no swell, cloudy, tide low & flowing 180 adults

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Figure A.1. Counts of adult Black Guillemots along the east coast of Foula, 1996-2015. Open symbols indicate

the lower count when two were made in a year (symbols overlap in 2015).

Atlantic Puffin. Puffins appear to have suffered a very serious decline since the previous season and were

relatively scarce this year. They were very late back, with the first ones seen onshore on 4th May. Although a

few were breeding, the usual large rafts of birds inshore were noticeably absent and birds appeared to be fishing far offshore. A small number of non-breeders (estimated at c.25% of the numbers in 2014) arrived on

15th July but were gone a few days later.

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SOTEAG ORNITHOLOGICAL MONITORING PROGRAMME€¦ · 2015. Statistics: number of counts, range, mean,...

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