SOTEAG ORNITHOLOGICAL MONITORING PROGRAMME

2013 SUMMARY REPORT

Martin Heubeck and Mick Mellor, Aberdeen Institute of Coastal Science and Management, University of Aberdeen.

January 2014

CONTENTS

Page 2013 Executive Summary 2

1. Monitoring of cliff-breeding seabirds 1.1. Weather 4 1.2. Northern Fulmar Fulmarus glacialis: Population counts 5 1.2. Northern Fulmar Fulmarus glacialis: Breeding success 6 1.3. European Shag Phalacrocorax aristotelis: Population counts 8 1.3. European Shag Phalacrocorax aristotelis: Breeding success 10 1.4. Black-legged Kittiwake Rissa tridactyla: Population counts 12 1.4. Black-legged Kittiwake Rissa tridactyla: Breeding success 13 1.5. Common Guillemot Uria aalge: Population counts 16 1.5. Common Guillemot Uria aalge: Breeding success at Sumburgh Head 18 1.5. Common Guillemot Uria aalge: Breeding success at Burravoe, Yell 21 1.6. Razorbill Alca torda: Population counts 22 1.6. Razorbill Alca torda: Breeding success at Sumburgh Head 23

2. Pre-breeding counts of Black Guillemots Cepphus grylle 24

3. Breeding Red-throated Divers Gavia stellata in Northmavine 27

4. Moulting Common Eiders Somateria mollissima in Yell Sound and Sullom Voe 28

5. Winter counts of diving seabirds and seaduck 5.1. Sullom Voe and Southern Yell Sound 29 5.2. Hascosay, Bluemull and Colgrave Sounds, and South Unst 30 5.3. Pool of Virkie to Bay of Quendale 31 5.4. Burra, Trondra and the Scalloway Islands 32

6. Beached Bird Surveys 6.1. Incidence of oiling 33 6.2. Non-oiled mortality 36

7. 2013 Publications and Presentations 38

8. Acknowledgements 38

Appendix 1. Seabird monitoring on Foula in 2013 39

1 2013 Executive Summary

1. Monitoring of cliff-breeding seabirds

Northern Fulmar Fulmarus glacialis. There was little change since 2012 in the number of apparently occupied sites (AOS) at the four colonies monitored. Breeding success at these colonies was relatively high: 0.48 ± 0.02 SE by the mean June count method, 0.55 ± 0.03 by the marked photograph method.

European Shag Phalacrocorax aristotelis. Non-breeding in southeast Mainland was even more extensive than in 2011-12. Counts from Sumburgh Head north to Mousa found 71% fewer nests (251, 42% active) than in 2010 (877, 97% active), and 52% fewer adults (593 vs. 1,244). The breeding season appeared more normal in southeast Yell where counts of adults (185) and nests (137, 91% active) were 17% and 22% lower than in 2009 (222 adults, 176 nests, 99% active). Along two stretches of coast on Fetlar, counts of adults (141) and nests (105, 72% active) were also only 23% and 17% lower than on the previous survey in 2002 (184 adults, 126 nests, 94% active). At Sumburgh Head, laying was late and very asynchronous, the proportion of nests that progressed to incubation (57%), and the proportion of these at which young were seen (16%) were the lowest yet recorded, as was breeding success (0.27 young fledged per laying pair). Laying was 5-6 weeks earlier at Burravoe, Yell, where 93% of nests progressed to incubation, chicks were seen at 64% of these, and success was a moderate 0.92.

Black-legged Kittiwake Rissa tridactyla. On Fetlar, there were 64 nests (91% active) at one breeding station, compared to 41 nests at three stations on the last visit, in 2002. The total of 149 nests (82% active) at southeast Yell was similar to the last visit (154), in 2009. In southeast Mainland, the total of 204 nests (65% active) at Mousa (deserted), No Ness, Troswick Ness and Boddam was almost half that in 2010 (392), while the total at Compass and Sumburgh Heads, and nearby Horse Island (499, 56% active) was 26% lower than in 2010 (673). The overall total of 1,059 nests counted in 2013 was 91% lower than at the same breeding stations in the baseline year of 1981 (11,947). Breeding success was monitored at six colonies. Laying was late, and most breeding attempts failed at the late incubation and early chick stages, in late June and early July. Success was zero at Sumburgh Head, No Ness and Hich Holm, 0.08 at Compass Head, 0.29 at Ramna Geo, and 0.12 at Burravoe, Yell; 2013 was the fourth successive year of extensive breeding failure.

Common Guillemot Uria aalge. Numbers were lower than in 2012 at the four colonies monitored, with 2013 population indices (1978 = 100) of 46.0 at Sumburgh Head, 39.5 at Troswick Ness, 1.5 at Esha Ness, and 41.8 at Burravoe, Yell. Colony attendance at Sumburgh Head was the most variable yet recorded, with a 50% difference in numbers in plots on 1st and 4th June, while a whole colony count there on 10th June recorded 6,279 birds, 14% fewer than on 11th June 2012 (7,307). Breeding success was monitored in single plots at Sumburgh Head and Burravoe, Yell. At Sumburgh, the proportion of regularly attended sites at which eggs were laid (63%) was the lowest yet recorded. Incubating birds seemed food-stressed, some abandoning eggs after apparent continuous shifts of 3-4 days. Only 11% of first eggs, and no relay eggs hatched and no chicks survived to fledge. Some chicks fledged from other parts of the colony but overall success was probably no higher than 0.05. At Burravoe, eggs were assumed to have been laid at only 58% of regularly attended sites, but chicks were seen at 40% of these, most survived to fledge, and success was estimated at 0.36 per laying pair, low by national standards but considerably higher than at Sumburgh.

Razorbill Alca torda. Plot counts at Sumburgh Head (2013 mean of 77 birds) suggest little change in numbers since 2007, after a 70% decrease during 2000-07, and a total colony count on 10th June was of 151 birds (189 on 11th June 2012). Few were present at the other colonies monitored, with mean counts of 2 at Troswick Ness, 5 at Esha Ness and 8 at Burravoe. Breeding success of 43 assumed or known egg-laying pairs at Sumburgh Head was 0.23, lower than in 2012 (0.56) but higher than in 2011 (zero).

2. Pre-breeding counts of Black Guillemots Cepphus grylle Counts were made at 12 of the 13 monitored stretches of coast. Along five sections, numbers were slightly (6-10%) lower than in 2012, markedly (23%) lower than in 2011 at one (Ronas Voe), and very similar (-1% to +3%) to 2011/12 at four; sea conditions meant counts on two sections were useless for monitoring purposes. Allowing for counts made in difficult conditions, numbers in 2011-13 were about 15-20% higher than in 2005-07.

2 3. Breeding Red-throated Divers Gavia stellata in Northmavine The number of breeding pairs (26), lochs with nests (30), and lochs with divers present (41) in the study area were the highest since the early 1980s. Eight pairs fledged 10 young, rather low success of 0.38.

4. Moulting Common Eiders Somateria mollissima in Yell Sound and Sullom Voe Counts from land located 494 birds in southern Yell Sound (7th August), all in Dales Voe and Colla Firth, and 118 in Sullom Voe (21st August), all in the northern half of the voe. Based on the 2012 census results, the total of 612 birds represented 13% of the Shetland population.

5. Winter counts of diving seabirds and seaduck Surveys of standard areas were made on four dates in January and early February (three by boat, one from land) and complemented counts made of other areas in December 2012. Counts exceeding Great Britain thresholds for sites of national importance were of 555 Long-tailed Ducks (threshold 110) in Colgrave Sound, 124 Red-breasted Mergansers (threshold 84) and 21 Slavonian Grebes (threshold 11) in Sullom Voe, 43 Great Northern Divers (threshold 25) between Pool of Virkie and Bay of Quendale, and 31 Great Northern Divers and 20 Slavonian Grebes around Burra, Trondra and the Scalloway Islands.

6. Beached Bird Surveys Of the total of 745 seabirds found dead during the year, 49 (6.6%) were oiled: 29 Fulmars, 4 Gannets, 3 Common Gulls, 5 Kittiwakes, 7 Common Guillemots. Eleven samples of oil were analysed: 2 were unrefined crude oils (1 Murchison/Statfjord, 1 Ninian), 9 were refined fuel oil residues. Few pelagic auks were found during winter 2012/13.

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 2013.

3 1. Monitoring of cliff-breeding seabirds

1.1. Weather Weather can influence the ability to carry out seabird monitoring, and in extreme cases, can directly affect seabirds’ breeding success. High pressure over Shetland in late March continued into early April, and the settled conditions allowed a good start to the pre-breeding counts of Black Guillemots. This broke down on 13th, after which a series of Atlantic lows brought wet and windy weather, allowing only one more morning of counting Black Guillemots, on 26th April. May began with a southwesterly severe gale, and while continued cool and unsettled weather throughout the month did not seem to cause any problems for breeding birds or hamper fieldwork greatly, it often made the latter unpleasant. The first 11 days of June were fairly dry and settled, allowing a good start to the population plot counts, while light south-westerly winds on 18- 19th enabled Zodiac surveys of Yell and Fetlar, the first survey of the latter for 11 years. Strong easterly winds and heavy rain on 22nd resulted in further losses of the few remaining eggs and chicks in the Common Guillemot breeding success plot at Sumburgh Head. Fog is the main hindrance to land-based fieldwork in summer, and some plot counts began an hour or two earlier than normal during June because of advancing fog banks. July was also a particularly foggy month, disrupting breeding success plot checks, but was also milder and drier than average.

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 2013.

Sumburgh Head Observer: Martin Heubeck Date Time (BST) Wind Sea state Cloud cover 1st June 2013 1340-1525 WNW 3 Calm 2/8 4th June 2013 1210-1330 NW 1 Calm 7/8 fog imminent 6th June 2013 1300-1430 NW 2 Slight swell 7/8 9th June 2013 1300-1435 E 1 Calm 7/8 16th June 2013 1100-1230 NW 3 Moderate swell 2/8 fog imminent

Troswick Ness Observer: Martin Heubeck Date Time (BST) Wind Sea state Cloud cover 1st June 2013 1000-1135 WNW 4 Calm 1/8 3rd June 2013 1000-1130 SW 3-4 Calm 8/8 occasional showers 6th June 2013 1000-1120 NW 3 Calm 5/8 9th June 2013 1000-1130 Calm Calm 7/8 13th June 2013 1000-1125 SSW 4 Moderate swell 8/8 occasional drizzle

Esha Ness Observer: Mick Mellor Date Time (BST) Wind Sea state Cloud cover 1st June 2013 1300-1400 NW 4 Heavy swell 6/8 6th June 2013 1315-1415 NW 2 Moderate swell 4/8 9th June 2013 1300-1400 NW 2 Slight swell 7/8 13th June 2013 1230-1330 SW 4 Moderate swell Fog 16th June 2013 1300-1400 NW 2-3 Slight swell 6/8

Burravoe, Yell Observer: Mick Mellor Date Time (BST) Wind Sea state Cloud cover 3rd June 2013 1000-1030 SW 3-4 Calm 7/8 6th June 2013 1000-1030 NNW 2 Slight swell 7/8 9th June 2013 0950-1020 NE 1 Calm 7/8 13th June 2013 0930-1000 SSE 3 Slight swell Fog imminent 16th June 2013 1000-1030 N 3 Slight swell 7/8

4 1.2. Northern Fulmar Fulmarus glacialis: Population counts

There was little change since 2012 in the number of adults or apparently occupied sites (AOS) at Troswick Ness or Burravoe, Yell, but a slight increase in the number of AOS at Sumburgh Head, and a slight decrease at Esha Ness (Table 1.2). The trend in numbers of AOS at these four colonies was very similar until the late 1990s (a gradual increase), but thereafter diverged at Esha Ness and Burravoe, but remained similar at Troswick Ness and Sumburgh Head (Figure 1.1).

Table 1.2. Mean counts of Fulmars and apparently occupied sites (AOS) at four Shetland colonies, 2012- 2013. Statistics: number of counts, range, mean, standard deviation, coefficient of variation, % change since 2012, and population indices for AOS (1978 = 100).

Colony Unit Year n Range Mean SD CV % ch. Index Sumburgh Birds 2012 5 261-325 286.2 26.10 0.09 Head 2013 5 280-299 290.6 9.81 0.03 +1.5 AOS 2012 5 193-220 204.2 10.03 0.05 139.2 2013 5 209-233 220.8 10.50 0.05 +8.1 150.5

Troswick Birds 2012 5 968-1177 1081.0 91.44 0.08 Ness 2013 5 994-1089 1051.2 36.33 0.03 -2.8 AOS 2012 5 748-859 796.8 41.14 0.05 129.1 2013 5 765-838 812.2 29.94 0.04 +1.9 131.6

Esha Ness Birds 2012 5 352-436 398.6 37.15 0.09 2013 5 341-393 370.8 23.21 0.06 -7.0 AOS 2012 5 270-313 289.0 19.74 0.07 120.1 2013 5 240-273 257.0 11.77 0.05 -11.1 106.9

Burravoe Birds 2012 5 221-239 233.0 7.38 0.03 2013 5 213-236 227.4 9.18 0.04 -2.4 AOS 2012 5 176-200 185.2 9.01 0.05 198.9 2013 5 181-191 186.4 3.85 0.02 +0.6 200.2

Figure 1.1. Annual index (1978 = 100) of Fulmar apparently occupied sites in study plots at four colonies, 1976-2013, and the mean index for the four colonies.

5 1.2. Northern Fulmar Fulmarus glacialis: Breeding success

This was measured by counting the number of chicks present in the population plots in mid August (just before the first is likely to fledge) and dividing the total by the mean June count of AOS (the method used since 1985), and also by the 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). While both methods will over-estimate the number of birds actually incubating, marking individual sites on large-format photographs is intended to minimise this but is still prone to uncertainty. What constitutes an AOS (when a bird appears to be sitting tightly on a reasonably horizontal area large enough to hold an egg) requires judgement by the observer. We used the same marked photographs as in 2012 and this year recorded sites as either (i) ‘no adult’, (ii) ‘adult(s) present’ but not qualifying as an AOS, or (iii) ‘AOS’. A second source of error is that an AOS can be overlooked, either through observer mistake or because the incubating adult is partly or wholly hidden by rocks or vegetation (large chicks are easier to detect in August because the site is surrounded by faeces and shed down). A third source of error is that some birds may not have laid an egg by the time of the three early visits. Chicks were counted on 13-14th August (Table 1.3), and were scored as small (mostly still covered in down), medium (c.50% covered in down) or large (little down left). None were seen dead, or believed to have fledged (evidenced by an empty site surrounded by faeces and down).

Table 1.3. The dates of visits to Fulmar plots, the total number of AOS marked onto photographs, the number qualifying as an AOS on each of three visits in May/June, the mean June count of AOS (see Table 1.2), 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 corresponding 2012 figures in brackets.

Sumburgh Head: 29/5, 31/5, 3-4/6, 13/8 Plot AOS 3 visits Mean Chicks Extra Success a (2012) Success b (2012) GSG 32 15 23.6 10 1 0.63 (0.50) 0.42 (0.41) GTS 163 133 155.6 82 2 0.61 (0.60) 0.53 (0.53) GPN 42 31 39.6 14 0 0.45 (0.52) 0.45 (0.46) Sum 237 179 218.8 106 3 0.58 (0.58) 0.48 (0.50) Mean 0.56 (0.54) 0.47 (0.47) ± SE 0.06 (0.03) 0.03 (0.03)

Troswick Ness: 29/5, 31/5, 3/6, 14/8 Plot AOS 3 visits Mean Chicks Extra Success a (2012) Success b (2012) BG 362 267 309.2 157 9 0.57 (0.45) 0.51 (0.41) SG 503.0 251 0.50 (0.46) Sum 812.2 408 0.50 (0.44) Mean 0.51 (0.44) ± SE 0.01 (0.03)

Esha Ness: 29/5, 1/6, 5/6, 14/8 Plot AOS 3 visits Mean Chicks Extra Success a (2012) Success b (2012) CG 208 130 173.6 62 13 0.43 (0.44) 0.36 (0.39) MC 31 24 26.6 11 0 0.46 (0.50) 0.41 (0.41) FG 52 31 50.2 24 9 0.60 (0.51) 0.48 (0.37) LST 6 5 6.6 3 2 0.43 (0.75) 0.45 (0.70) Sum 297 190 257.0 100 24 0.47 (0.47) 0.39 (0.40) Mean 0.48 (0.55) 0.43 (0.47) ± SE 0.04 (0.07) 0.03 (0.08)

Burravoe: 28/5, 30/5, 3/6, 14/8 Plot AOS 3 visits Mean Chicks Extra Success a (2012) Success b (2012) 206 148 186.4 95 12 0.59 (0.30) 0.51 (0.29)

6 Of the three ‘extra’ AOS at Sumburgh, one was scored incorrectly as ‘adult’ on the 3rd check, one was overlooked on one check, and one was marked as ‘hidden?’ on one check; breeding success in the two smaller plots was lower than in 2012 in one, and higher in the other, but overall very similar.

At Troswick Ness, the nine ‘extra’ AOS comprised three with unattended eggs (two broken), two scored incorrectly as ‘adult’ on the 2nd and 3rd checks, and four that had been overlooked on one or more checks because the incubating adult was difficult to see. Both measures of breeding success were higher than in 2012 in both geos. No mammalian predators were seen in either geo (cats and ferrets have been seen in the past), but the remains of five Fulmars were seen on the cliff top or slopes in May and June. In Brei Geo the ‘north lower’ grass and boulder section continues to have low numbers of AOS and chicks (mean June count of 69 AOS, 65 scored as AOS on 3 checks, 23 chicks in August, success = 0.33/0.35); this section has had consistently low success since 2000 (mean June count of 171 AOS, 90 chicks in August, success of 0.53).

At Esha Ness, 24 sites with chicks in August were not scored as AOS on each of the three earlier checks. Of these, seven had adults present on all three checks and may have been scored wrongly as not qualifying as an AOS on one or more occasion. The remaining 17 had no adult present on one or more checks, including nine with no adult on the third check, which would suggest late laying. Most of these 17 sites were close to the cliff top or near the narrow heads of Calders Geo and ‘Fulmar Geo’ where they can be viewed from the cliff top at close range. The number of people walking the Esha Ness cliffs during spring and summer has increased considerably since the plots were established and unintentional disturbance may be affecting Fulmars breeding at some locations. Both measures of breeding success were slightly lower than in 2012.

Of the 12 ‘extra’ sites at Burravoe, five had adults present on each of the three early checks and may have been scored incorrectly, while the remainder had no adults recorded on one (5) or two (2) checks. Breeding success by the June count method was the highest since monitoring began in 2003, with the number of chicks present in August being equaled only in 2010.

Fulmar breeding success has previously been particularly low in years when other seabird species have experienced major breeding failures (1988, 1990, 2004, 2008), and it is perhaps surprising that success should have been so high in 2013 (Figure 1.2). However, these measures do not take account of any variation in the extent of non-breeding by lower quality individuals or at lower quality sites. The marked photograph method suggests mean breeding success at the four colonies was 20% higher than in 2012 yet only 12% more chicks were present in August 2013 (and most of this difference was accounted for by Burravoe), while the number of pairs laying (AOS on three dates + ‘extras’) was 9% lower than in 2012, and 14% fewer sites were scored as an AOS on at least one check.

Figure 1.2. Mean Fulmar breeding success (± SE) at 3-4 monitored colonies, 1985-2013 (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).

7 1.3. European Shag Phalacrocorax aristotelis: Population counts

As in 2012, land-based counts in May at Sumburgh Head and No Ness, plus the breeding success monitoring at the former, indicated 2013 would be a late season and probably with extensive non-breeding, at least in southeast Mainland (Figure 1.3). Indeed, No Ness was virtually deserted on 15th May, with just 34 adults present at former nest sites (none in roosts), and one incubating, eight empty and three trace nests visible. In 2012, and in marked contrast to the situations at Sumburgh Head and No Ness, boat surveys of the southwest and west coasts of Shetland found that the number of Shag nests was similar to 2009 (Table 1.4), although nest-building and laying had clearly been much later than in 2009. A priority in 2013 was therefore to assess breeding numbers along the east coast of Shetland.

Figure 1.3. Census counts from land of adult Shags and nests at Sumburgh Head and No Ness in 2010-13: nests apparently with eggs or chicks (black); empty, well-built nests (blue); trace nests (red); adults at breeding sites in addition to the number of nests (white); roosting adults away from breeding sites (grey).

On 19-20th June, Zodiac surveys were made of the three stretches of coast on Fetlar and Yell for which detailed, mapped counts of Shag nests existed (Table 1.4). Fetlar had not been visited since 2002, but southeast Yell was last surveyed in 2009. In ‘normal’ breeding seasons, at least 90% of Shag nests are usually recorded as active (i.e. apparently with eggs or chicks) on June surveys by Zodiac, while the more critical use of a telescope probably results in slightly lower proportions for land-based counts. At both Strandburgh Ness (the northeast corner of Fetlar) and Lambhoga (the southwest corner) the total number of nests was 16% fewer than in 2002 but the proportion active was distinctly lower, particularly at Strandburgh Ness where some nests had large young, but many others consisted only of scattered scraps of grass and seaweed. On four surveys of southeast Yell in the 2000s, the highest nest count was in 2009, and while the 2013 total was 22% lower than this, 91% of nests were active including many with large young.

The coast from Mousa south to Virkie was surveyed by Zodiac on 25-26th June, and the contrast with southeast Yell was striking. On Mousa there were only 16 active nests compared to 110 in 2010 (-85%), while across Mousa Sound at No Ness the respective figures were 35 and 288 (-88%); no chicks were seen at either location. The small number of nests at nearby Cumlewick Ness was similar to 2009-10, but only seven were active. Along the coast from Troswick Ness to Virkie, only 23 active nests were found compared to 161 in 2010 (-86%). Totals for the surveyed coasts from Mousa to Sumburgh Head in 2013 were 593 adults at nest sites (1,244 in 2010, -52%), 105 active nests (851 in 2010, -88%), 45 well-built but empty nests (14 in 2010, +221%), and 101 trace nests (12 in 2010, +742%).

It had been hoped in 2013 to survey two other coasts with large concentrations of Shags, Out Skerries (most recent count of 185 nests in 2001) and Papa Stour (299 nests in 2006), but time and sea conditions did not allow this. At the time of the Seabird 2000 census (1998-2002), Shetland held 29% of the Scottish, 19% of the British and Irish, and 7-8% of the World breeding populations of Shags (Mitchell et al. 2004. Seabird Populations of Britain and Ireland. Poyser, London.). While these single-day Zodiac surveys cannot record potential breeding numbers, they can give an indication of the degree and geographic extent of this current level of non-breeding.

8

Table 1.4. Counts from the sea of all Shag nests (trace, empty, and active, i.e. apparently incubating or containing chicks) in June along coasts surveyed in 2011-13, the percentage of nests that were active, and the count date. For land counts at No Ness and Sumburgh Head, where more than one was made in a year those closest to mid June are given, except if the earlier count of active nests was higher (*).

Coastline 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Strandburgh Ness, 82 70 59 Fetlar 95% 96% 68% 23/6 21/6 20/6 Lambhoga, Fetlar 55 46 93% 78% 21/6 20/6 Southeast Yell 151 134 143 176 137 99% 95% 99% 99% 91% 21/6 29/6 16/6 22/6 19/6 Mousa 71 94 109 113 26 90% 89% 86% 97% 62% 12/6 20/6 21/6 22/6 25/6 No Ness (land) 144 138* 125* 103 124 139 150 138 185* 204 134* 54 49 90% 87% 78% 87% 83% 97% 95% 94% 89% 95% 84% 48% 47% 30/5 28/5 27/5 15/6 14/6 13/6 22/6 13/6 23/5 9/6 10/6 No Ness (sea) 196 144 177 207 271 295 80 90% 94% 79% 94% 97% 98% 44% 9/6 12/6 20/6 4/6 21/6 22/6 25/6 Cumlewick Ness 10 13 14 13 12 11 100% 77% 93% 100% 100% 64% 12/6 20/6 4/6 21/6 22/6 25/6 Troswick to Virkie 169 175 122 114 149 165 167 61 96% 92% 89% 86% 93% 96% 96% 38% 9/6 12/6 12/6 20/6 4/6 13/6 16/6 26/6 Sumburgh Head (land) 263* 252 221 207* 166* 233 213 215 223 290 100* 85* 73 96% 97% 95% 86% 83% 97% 99% 98% 93% 97% 67% 54% 33% 31/5 12/6 6/6 27/5 5/6 13/6 22/6 13/6 16/6 8/6 27/5 30/5 10/6 Roo Geo, Siggar Ness 41 47 9 100% 96% 89% 9/6 11/6 27/6 St Ninian’s Isle 53 59 50 96% 93% 82% 9/6 11/6 27/6 South Havra 49 57 53 90% 89% 58% 9/6 11/6 27/6 Kettla Ness 58 51 57 51 51 97% 96% 89% 94% 82% 6/6 16/6 9/6 11/6 27/6 Skelda Ness – 263 219 300 210 278 291 Culswick 96% 85% 96% 96% 91% 85% 15/6 11/6 27/6 21/6 9/6 20/6 Vaila 136 89 126 94 112 104 99% 66% 96% 97% 97% 92% 15/6 11/6 27/6 21/6 9/6 20/6 Muckle Roe 76 63 62 93 67 97% 83% 89% 94% 58% 8/6 10/6 7/6 23/6 9/6

9 1.3. European Shag Phalacrocorax aristotelis: Breeding success

This was monitored in the same 14 plots at Sumburgh Head as in 2008-12 (38 checks, 8th April to 5th October), and the same three plots at Burravoe, Yell as in 2012 (36 checks, 9th April to 22nd August: Table 1.5). Timing of laying at Sumburgh Head was the latest yet recorded, with the first apparently incubating bird seen on 29th April (Figure 1.4). As in 2012, there was a complete lack of synchrony to the breeding season, the status of many nest sites alternated between apparently incubating to empty or trace, and of the 56 nest sites which did achieve apparently incubating status, at 19 (34%) it was recorded as such on only one check during the season. The percentage of all nests that achieved apparently incubating status, the proportion at which chicks were seen, and breeding success were all the lowest yet recorded at Sumburgh Head (Figure 1.5).

Figure 1.4. 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, 1996-2013. 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 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

10 At Burravoe, there were seven apparently incubating nest sites on the first check on 9th April (19% of the total for the season) and timing of laying was 5-6 weeks earlier than at Sumburgh Head, with incubation first recorded at 25% of nests by 12th April (21st May at Sumburgh), 50% by 25th April (9th June at Sumburgh), and 75% by 3rd May (26th June at Sumburgh; Figure 1.4). Incubation was recorded at a high proportion of sites, but there seemed to be many early clutch losses and continuous incubation to hatching was recorded at only 13 (33%) sites. The first chicks were seen on 16th May, over seven weeks earlier than at Sumburgh (7th July), and the proportion of nests at which chicks were known to have hatched was markedly higher than at Sumburgh Head. While three whole unfledged broods disappeared and chicks were known to have been lost from a further three nests, breeding success was moderately high, and the 36 young fledging included four broods of three (Table 1.5).

The two main determinants of Shag breeding success at Sumburgh Head have been apparent low food availability, and heavy swell washing away nests. The latter was the case in 1999, 2000 and 2010, whereas low food availability was largely responsible for relatively low success in 1990, 2004 and 2005, when very few pairs managed to fledge three chicks (Figure 1.5). The number of incubated nests in plots in 2013 was 75% lower than in 2010, and assuming that most of the adults that bred in 2010 are still alive, it is probable that only higher quality individuals attempted to breed in 2013. Even these birds appear to have struggled with adverse conditions, with few hatching chicks and, for the first time on record, none fledging a brood of three young.

Figure 1.5. Shag breeding parameters at Sumburgh Head, 1988-2013. Upper: chicks fledged per incubated nest. Lower: The percentage of: (i) nests that progressed to incubation (blue), (ii) incubating nests where chicks were known to have hatched (red), (iii) laying pairs that fledged a brood of three chicks (green).

11 1.4. Black-legged Kittiwake Rissa tridactyla: Population counts

Colonies in Fetlar and southeast Yell were surveyed by Zodiac on 19-20th June (Table 1.6). Fetlar had not been surveyed since 2002, and it is not known when breeding ceased at Strandburgh Ness, but the count of 64 nests (91% incubating, or active) at Lambhoga was the highest since 1986 (67). In southeast Yell, adults from Whitehill have probably fuelled the regrowth of the single colony at the Horse of Burravoe; there was little change at Ladies Hole since 2009, but a 115% increase over the past decade; 82% of nests in southeast Yell were active. Colonies from Mousa to Horse Island were surveyed by Zodiac on 25-26th June. The number of nests and adults were substantially lower than in 2010, while the proportions of incubating nests (65% in southeast Mainland, 56% in the Sumburgh area) were lower than in Yell or Fetlar. All nests are counted on Zodiac surveys, but evidence of nest building and laying is harder to detect on a single survey in some years. In the Sumburgh Head success plots in 2010, when 85% of nest-building pairs laid, 87% of all nests were present in some form on 14th June, two days before the Zodiac survey, and 97% of laying pairs still had active nests. In 2013, when only 64% laid, the respective figures on the day before the survey were 70% and 63%. A count at Foula on 10th June (AON only) showed a further decline; the decrease there of 93% since 1981 was similar to that for southeast Mainland and the Sumburgh area combined (91%).

Table 1.6. Counts of Kittiwake nests (incubating, empty and trace) and adults at breeding stations surveyed in 2013, compared with counts in 1981 (used as a baseline), and from 2004 (2002 in the case of Fetlar).

Fetlar 1981 2002 2005 2006 2007 2008 2009 2010 2011 2012 2013 Clett Stack 30 0 0 Strandburgh Ness 273 24 0 Southeast Fetlar 32 8 0 Lambhoga 37 9 64 Total nests 372 41 64 % change p.a. +3.5 Total adults 656 63 79

Southeast Yell 1981 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Vatsetter/Birrier 82 0 0 nc 0 Whitehill 0 46 58 35 1 Horse of Burravoe 259 0 0 4 36 Ladies Hole 133 52 82 115 112 Total nests 474 98 140 154 149 % change p.a. +19.5 +3.2 -0.8 Total adults 805 113 166 220 155

SE Mainland 1981 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Mousa 148 3 nc 16 14 0 No Ness 1768 260 251 269 314 165 Troswick Ness 716 58 63 61 27 19 Boddam 256 43 28 35 37 20 Total nests 2888 364 342 381 392 204 % change p.a. -6.0 +3.7 +2.9 -19.6 Total adults 3944 458 448 511 468 309

Sumburgh area 1981 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Compass Head 464 124 152 146 163 90 Sumburgh Head 2177 356 354 354 386 210 Horse Island 594 14 31 65 50+ 15 Total nests 3235 494 537 565 599+ 315 % change p.a. +4.3 +2.6 +6.0 -19.3 Total adults 5361 617 686 896 673+ 499

Foula 1981 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 4978 942 898 1065 997 509 582 480 378 327 % change p.a. -4.7 +18.6 -6.4 -28.5 +14.3 -17.5 -21.3 -13.5

12 1.4. Black-legged Kittiwake Rissa tridactyla: Breeding success

This was monitored at the same five colonies as in 2012, but with the addition of Hich Holm, which can be viewed at a distance of 300 m from the west cliffs of St Ninian’s Isle. Laying was again late, with the date by which 50% of pairs had laid ranging from 3rd to 10th June (Table 1.7, Figure 1.6). There was again a high element of non-breeding, with the proportion of nests started that progressed to incubation ranging from 62- 76% (Table 1.8).

Chicks were known to have hatched at all colonies except No Ness, where breeding numbers are now very low, but only two broods of two chicks were seen, at Burravoe on 27th June and at Sumburgh Head on 11th July; none of these four chicks survived to fledge. Most breeding failures occurred around the late incubation and early chick stages, and figures for the percentage hatched and the percentage of hatched nests with dead young will be minima. At Sumburgh Head, the first chicks were seen on 3rd July, by which time 43% of breeding attempts had failed, but this rose to 90% by 19th July, when eight chicks remained, but none survived. The pattern was similar at Compass Head and Hich Holm. At Ramna Geo, however, although the failure rate increased from 47% by 4th July (first chick date) to 70% by 18th July, there were no further losses and ten chicks fledged. Laying at Burravoe had been slightly earlier and the first chicks were seen on 27th June. In early July, the nest failure rate increased from 22% on 4th to 65% by 18th, but only three chicks were lost after this and 12 fledged, with seven still present on the last check on 14th August.

Table 1.7. Dates by which 20%, 50% and 80% of Kittiwakes had laid at monitored colonies, 2011-2013.

Sumburgh Head Compass Head No Ness 2011 2012 2013 2011 2012 2013 2011 2012 2013 20% 20/5 27/5 1/6 3/6 29/5 31/5 24/5 29/5 31/5 50% 27/5 1/6 6/6 8/6 3/6 6/6 29/5 4/6 4/6 80% 6/6 7/6 11/6 12/6 10/6 10/6 9/6 11/6 5/6 Hich Holm, St Ninian’s Ramna Geo, Burra Burravoe, Yell 2013 2011 2012 2013 2011 2012 2013 20% 3/6 5/6 1/6 6/6 25/5 29/5 27/5 50% 7/6 10/6 9/6 10/6 1/6 2/6 3/6 80% 14/6 16/6 13/6 15/6 9/6 12/6 8/6

Figure 1.6. Dates by which 50% of Kittiwakes breeding that year were presumed to have laid their first eggs at colonies monitored by SOTEAG, 1989-2013, from north (Burravoe, Yell) to south (Sumburgh Head).

13 Table 1.8. The number of Kittiwake nests and occupied sites at monitored colonies 2004-2013; 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 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Total nests 117 128 156 163 148 177 177 145 139 138 Incubating 85 111 144 128 89 128 151 94 93 89 % Incubating 72.6 86.7 92.3 78.0 60.1 72.3 85.3 64.8 66.9 64.5 Sites adult(s) only 33 20 4 20 36 39 22 39 35 40 % Nests hatched 40.0 90.1 89.6 82.8 21.3 80.5 86.8 21.3 60.2 32.6 % Nests hatched b/2 0 45.0 34.1 17.9 5.3 24.3 11.5 15.0 1.8 0 % Hatched with dead 17.6 2.0 8.5 12.3 5.3 3.9 8.4 10.0 26.8 20.7 % Nests failed 97.6 14.4 26.4 46.9 98.9 44.5 88.1 100 84.9 100 Chicks fledged 2 129 125 69 1 75 18 0 14 0 Sum success 0.02 1.16 0.87 0.54 0.01 0.59 0.12 0 0.15 0 Mean success 0.008 1.21 0.70 0.47 0.51 0.11 0 0.13 0 SE 0.008 0.07 0.14 0.08 0.09 0.06 0.04

Compass Head 2008 2009 2010 2011 2012 2013 Total nests 61 62 55 21 24 21 Incubating 37 41 41 10 18 13 % Incubating 60.7 66.1 74.5 47.6 75.0 61.9 Sites adult(s) only 3 5 2 6 8 5 % Nests hatched 13.5 65.9 73.2 30.0 38.9 30.8 % Nests hatched b/2 0 17.9 13.3 0 14.3 0 % Hatched with dead 0 14.3 53.3 0 0 50.0 % Nests failed 100 56.1 100 100 88.9 100 Chicks fledged 0 19 0 0 3 1 Sum success 0 0.46 0 0 0.17 0.08

No Ness 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Total nests 41 28 30 31 43 45 50 29 22 19 Incubating 33 23 26 23 32 39 38 21 16 14 % Incubating 80.5 82.1 86.7 74.2 74.4 86.7 76.0 72.4 72.7 73.7 Sites adult(s) only 14 7 4 2 14 0 0 8 9 5 % Nests hatched 0 87.0 84.6 87.0 40.6 74.4 50.0 38.1 31.3 0 % Nests hatched b/2 0 25.0 27.3 10.0 0 34.5 15.8 0 0 0 % Hatched with dead 0 10.0 13.6 15.0 7.7 6.9 5.3 0 20.0 0 % Nests failed 100 21.7 26.9 82.6 75.0 51.3 100 100 100 100 Chicks fledged 0 19 20 4 8 23 0 0 0 0 Sum success 0 0.83 0.77 0.17 0.25 0.56 0 0 0 0

Hich Holm 2013 Total nests 58 Incubating 38 % Incubating 67.9 Sites adult(s) only 5 % Nests hatched 13.2 % Hatched b/2 0 % Hatched with dead 0 % Nests failed 100 Chicks fledged 0 Sum success 0

14 Table 1.8. continued.

Ramna Geo, Burra 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Total nests 81 98 110 124 91 111 117 76 64 48 Incubating 55 82 101 100 55 81 74 45 24 34 % Incubating 67.9 83.7 91.8 80.6 60.4 73.0 63.2 59.2 37.5 70.8 Sites adult(s) only 24 8 7 6 16 14 11 22 15 8 % Nests hatched 41.8 65.9 84.2 80.0 16.9 85.2 18.9 2.2 0 35.3 % Hatched with b/2 4.3 25.9 22.4 30.0 10.0 62.3 7.1 0 0 0 % Hatched with dead 9.1 1.9 1.2 7.5 0 0 14.3 0 0 8.3 % Nests failed 63.6 36.6 22.5 30.0 83.1 17.3 98.6 100.0 100.0 70.6 Chicks fledged 19 62 94 80 11 103 1 0 0 10 Sum success 0.35 0.76 0.92 0.80 0.19 1.27 0.01 0 0 0.29

Burravoe, Yell 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Total nests 52 73 89 104 98 113 135 117 128 130 Incubating 47 66 80 94 85 99 107 87 94 99 % Incubating 90.4 90.4 89.9 91.0 86.7 87.6 79.3 74.4 73.4 76.2 Sites adult(s) only) 2 2 1 1 7 4 8 12 9 15 % Nests hatched 72.3 78.8 85.0 87.2 34.1 72.7 69.2 28.7 51.1 40.4 % Hatched with b/2 5.9 36.5 30.9 25.6 34.5 51.5 6.8 8.0 43.8 2.5 % Hatched with dead 2.9 0 2.9 4.9 0 1.4 8.1 4.0 2.1 15.0 % Nests failed 31.9 21.2 25.0 26.6 72.9 35.4 53.3 78.2 59.6 87.9 Chicks fledged 33 70 76 81 33 95 52 20 49 12 Sum success 0.70 1.06 0.95 0.86 0.39 0.96 0.49 0.23 0.52 0.12

The mean annual figure for Kittiwake breeding success over the 28 years of monitoring has been 0.38 chicks fledged per laying pair, less than half the figure of 0.80 which might be required to replace adult and immature mortality (Coulson 2011. The Kittiwake. Poyser, London). Since 2013 was the fourth successive year of very low productivity, a further decline in breeding numbers through low recruitment (at least) seems inevitable (Figure 1.7).

Figure 1.7. Mean Kittiwake breeding success (+ SE) at colonies (4-7 per year) monitored by SOTEAG, 1986-2013.

15 1.5. Common Guillemot Uria aalge: Population counts

Numbers at Troswick Ness were similar to 2012, with little variation between counts (Table 1.9). At the other three colonies monitored, numbers were considerably lower than in 2012 and counts were highly variable. Of three plots at Burravoe, numbers were 23% lower than in 2012 at two, but in the third plot (mean 2012 count of 76.2 birds) just 3-15 birds were recorded. The mean count at Sumburgh Head in 2013 was 72% lower than the peak in 2000, with respective figures of -45% at Troswick Ness, -98% at Esha Ness and -33% at Burravoe. The mean population index in 2013 (32.2) was the lowest yet recorded (Figure 1.8).

At Sumburgh Head, the 50% difference between count totals on 1st June (749 birds) and 4th June (376) was the greatest yet recorded at this colony (Table 1.10). Numbers were low in all plots on 4th June, but the Smithfield Geo plot (where on 1st June almost all birds were standing up) was virtually deserted, with a single rolled egg the only evidence of breeding. Most of this plot is smooth, steeply sloping rock face with few deep ledges or crevices, and given the mass desertion and egg loss observed in the breeding success plot (see p. 18), it would seem more likely that major egg loss had occurred (whether catastrophic or persistent) rather than few birds had laid. On 23rd June, nine birds were apparently incubating (see Table 1.13, p.19).

A total of 6,279 adult Guillemots were counted from land at Sumburgh Head on 10th June, 14% fewer than the 7,307 counted on 11th June 2012 (Figure 1.9). Since these census counts became annual in 2007, they have generally recorded changes in the same direction as the counts in study plots, but the difference between the two values has exceeded 10% in four of the past six years (Table 1.11).

Table 1.9. Mean counts of individual Common Guillemots in study plots at four Shetland colonies, 2012 and 2013. Statistics are: number of counts, range, mean, standard deviation, coefficient of variation, percentage change since 2012, and population indices (1978 = 100).

Colony Unit Year n Range Mean SD CV % ch. Index Sumburgh Birds 2012 5 682-877 812.2 79.56 0.10 61.2 Head 2013 5 376-749 610.6 141.84 0.23 -24.8 46.0

Troswick Birds 2012 5 193-277 226.4 33.97 0.15 41.2 Ness 2013 5 194-226 217.0 14.27 0.07 -4.2 39.5

Esha Ness Birds 2012 5 40-69 57.8 12.07 0.21 8.3 2013 5 2-23 10.4 8.17 0.79 -82.0 1.5

Burravoe Birds 2012 5 213-271 248.6 21.97 0.09 74.4 2013 5 110-175 139.6 25.45 0.18 -43.8 41.8

Figure 1.8. Annual index (1978 = 100) of Common Guillemot numbers in study plots at four monitored colonies, 1976-2013, and the mean index for the four colonies.

16 Table 1.10. The mean count in 2000, and details of the five counts in 2013 at the eight Common Guillemot population monitoring plots at Sumburgh Head, with mean, coefficient of variation, and the percentage difference between the highest and lowest count. Details are given for the breeding success plot, and the three previous most variable sets of counts, in 1997, 2002, and 2012.

Sumburgh Head 2000 2013 counts 2013 Percentage Population plot mean 1/6 4/6 6/6 9/6 16/6 mean (cv) difference Greystane Geo 70.8 17 8 15 20 13 14.6 (0.31) - 60% Geo of Toun South 134.6 64 49 63 62 63 60.2 (0.10) - 23% Geo of Toun North 284.4 49 25 58 62 51 49.0 (0.29) - 60% Little Tind East 228.2 120 81 104 125 110 108.0 (0.16) - 35% Little Tind West 109.4 45 22 35 30 30 32.4 (0.26) - 51% Guillemot Stack 308.4 111 68 85 101 95 92.0 (0.18) - 39% Shoulder 479.2 178 108 166 182 166 160.0 (0.19) - 41% Smithfield Geo 553.1 165 15 77 101 114 94.4 (0.58) - 91% Total 2168.1 749 376 603 683 642 610.6 (0.23) - 50% Success plot 128 105 136 100 127 119.2 (0.13) - 26%

1997 Totals 1672 1754 1813 2046 2081 1873.2 (0.10) - 20% 2002 Totals 1166 1226 1430 1406 1539 1353.4 (0.11) - 24% 2012 Totals 682 793 865 877 844 812.2 (0.10) - 22%

Figure 1.9. 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 multiple counts in eight study plots.

Table 1.11. Year-to-year changes in Common Guillemot numbers at Sumburgh Head, as recorded by the mean of five counts in study plots, and a single count of the entire colony.

Years Plot counts Colony count Difference 2007-08 -11.0% +2.5% 13.5% 2008-09 +12.2% +8.3% 3.9% 2009-10 -6.7% -10.4% 3.7% 2010-11 -17.6% -30.2% 12.6% 2011-12 +10.8% +47.3% 36.5% 2012-13 -24.8% -14.1% 10.7%

17 1.5. Common Guillemot Uria aalge: Breeding success at Sumburgh Head

This was again monitored (by MH) in a single plot on the east side of the Head, which was checked daily from 10th April to 7th July, with the number of adults present at the time of the check (usually 08.30-10.00 BST) recorded. There were 182 birds present on 10th April and 169 on 11th April, then none until 193 on 20th April (Figure 1.10). The first egg was seen on 7th May, three days later than in 2012, and median laying date of 19th May was five days later than in 2012 (Table 1.12).

By 25th May, 28 (40%) of 70 first eggs had been lost. Many incubating birds seemed food-stressed, and at least eight eggs were abandoned in situ during 18-25th May, several after 4-6 days of apparently continuous incubation (e.g. by a very dirty member of a mixed bridled/non-bridled pair). Birds also appeared generally nervous, with many non-incubators standing up if a bird flew into the breeding group, and a number of eggs were seen to have been lost during fights between neighbours. When the plot was checked early on the morning of 26th May, seven birds sitting tight remained to be checked later in the day for newly laid eggs, but on return at 14.00 h the plot was virtually deserted with unattended eggs both in situ and rolled off-site. Birds quickly began flying back in, but 19 eggs had been definitely lost and three had probably been laid since the previous afternoon and lost (based on the dates of probable relays). The cause of this mass-panic would have remained unknown had not Paul Harvey seen a Rabbit wander close to the breeding group 20 minutes earlier, which prompted virtually all birds in the plot and the surrounding area to fly away. Similar mass-panic (although to a lesser degree) was seen on several other occasions. Typically, birds (including some of those incubating) would begin head-bobbing and standing up for no apparent reason, gradually moving towards the edge of the breeding group before either settling down again or flying offshore. Such behaviour, which has not been seen in previous years, undoubtedly contributed to the high rate of egg loss (only 11% of first eggs, and none of the 34 relay eggs were known to have hatched; Table 1.14).

Table 1.12. Common Guillemot breeding parameters and success in a study plot at Sumburgh Head, 2003- 2013, calculated as young fledged (a) per regularly attended site and (b) per site at which eggs were laid.

2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Attended sites 148 144 162 163 165 166 169 169 164 163 155 Sites with egg laid 123 108 117 136 142 137 144 154 142 140 98 % sites laid 84% 75% 72% 83% 86% 83% 85% 91% 87% 86% 63% First egg date 10/5 13/5 11/5 8/5 4/5 4/5 2/5 2/5 29/4 4/5 7/5 Median laying date 21/5 23/5 26/5 19/5 11/5 16/5 10/5 9/5 9/5 14/5 19/5 % Hatched first egg 56% 31% 50% 62% 66% 49% 65% 68% 21% 68% 11% Chicks fledged 36 9 66 78 80 39 91 78 2 55 0 Fledged/site 0.24 0.06 0.41 0.48 0.48 0.23 0.54 0.46 0.01 0.34 0.00 Fledged/egg 0.29 0.08 0.56 0.57 0.56 0.28 0.63 0.51 0.01 0.39 0.00

When the plot was checked at 09.00 on 23rd June, just after 24 hours of persistent rain had stopped, 23 birds were incubating or brooding: 13 on first eggs, 5 on relays and 5 with chicks. All other 64 birds were standing up (to avoid contaminating their plumage in guano) and the proportion of birds ‘sitting tight’ in other parts of the colony, including some of the population plots, was quickly checked before the cliffs dried off (Table 1.13). The lowest proportion was in the Geo of Smithfield plot, a relatively smooth and steep rock face, and the highest proportions were in the Little Tind East plot, where most birds nest on broad horizontal ledges capable of holding several pairs deep, and in Shag Site 2, where many pairs nest in deep grooves in the rock. It seems probable that cliff micro-topography, and its influence on the chances of unattended eggs remaining in situ, was an especially important factor in the extent of egg loss this year.

18 Table 1.13. The proportion of Common Guillemots ‘sitting tight’ (and almost certainly on eggs or chicks) in nine areas of the Sumburgh Head colony, between 09.20 and 11.00 on 23rd June 2013.

Plot / area ST / Birds = % on eggs/chicks Success plot 23 / 87 = 26%

Surrounding the success plot 76 / 199 = 38%

Shag Site 2 214 / 526 = 41%

Geo of Toun South plot 18 / 54 = 33%

Little Tind East plot 53 / 104 = 51%

Little Tind West plot 10 / 28 = 36% Rest of Little Tind 32 / 104 = 31 % Geo of Smithfield plot 9 / 184 = 5% Smithfield Stack 45 / 128 = 35%

Of the 11 chicks that hatched, seven were lost after 1-4 days, two after six days, one after 11 days and the oldest after 14 days. The maximum number alive on one day was seven on 20-21st June, too few to conduct meaningful feeding watches. By 1st July there were no chicks left in the plot and by 4-6th July the only adult present was on a late first egg, which it had lost by 7th July. Although some other areas of the colony were similarly deserted by mid July, up to 2,000 very vocal adults were present on the west side of the Head until late July and a small but diminishing proportion were brooding chicks, including some large enough to fledge. These loafing adults had gone by 1st August, and the last (single) adult (with a chick too under- developed to have fledged) was seen on 16th August. Herring and Great Black-backed Gulls patrolled the colony throughout this period and were seen taking chicks, but some undoubtedly did fledge. The single breeding success plot was clearly not representative of the colony as a whole, but overall productivity at Sumburgh Head was almost certainly below 0.10 and probably below 0.05 fledged per laying pair.

Figure 1.10. Upper: The daily number of eggs, chicks and adult Common Guillemots in the breeding success plot at Sumburgh Head in 2013. Lower: The number of eggs and chicks missing from the previous day, or known to have been lost that day.

19 Table 1.14. Causes (%) of breeding failure of Common Guillemots at Sumburgh Head, 2008-13.

2008 2009 2010 2011 2012 2013 Number of failed breeding attempts 98 53 76 140 85 98 Lost first egg before possible hatching (< 29 days), no relay 39.8 35.8 19.7 31.4 24.7 50.0 Lost first egg around possible hatching (29-37 days), no relay 17.3 7.5 3.9 6.4 4.7 4.1 Presumed infertile first egg, incubated 38+ days 2.0 11.3 13.3 0.7 1.2 0 Lost relay egg before possible hatching (< 29 days) 11.2 20.8 11.8 25.7 11.8 34.7 Lost relay egg around possible hatching (29-37 days) 1.0 0 3.9 5.0 3.5 0 Presumed infertile relay egg, incubated 38+ days 0 0 0 0.7 1.2 0 Lost first egg chick before presumed fledging 27.6 17.0 36.8 20.0 50.6 11.2 Lost relay chick before presumed fledging 1.0 7.5 10.5 10.0 2.4 0

Since 2000, adult Guillemots in the breeding success plot have been counted at a set time on the same afternoons as the population counts, giving a measure of colony attendance per regularly attended site and per breeding pair during the season, and per incubating or brooding adult on the day (Table 1.15). In 2013, the number of birds present per regularly attended site was the lowest yet recorded, while the number per breeding pair increased because the proportion of sites at which an egg was laid was also the lowest yet recorded (Figure 1.11, Table 1.12).

Table 1.15. Details of counts of Common Guillemots in the Sumburgh Head breeding success plot in 2013 (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 2013 1/6 4/6 6/6 9/6 16/6 Mean SD Time (BST) 1350 1220 1310 1310 1110 Total birds in plot (n) 128 105 136 100 127 119.2 15.74 Total regularly attended sites (a) 155 155 155 155 155 Total breeding pairs (b) 98 98 98 98 98 No. of eggs or chicks on count date (c) 38 34 40 33 38 k-value (a/n) 1.21 1.48 1.14 1.55 1.22 1.32 0.18 k-value (b/n) 0.77 0.93 0.72 0.98 0.77 0.83 0.11 k-value (c/n) 0.30 0.32 0.29 0.33 0.30 0.31 0.02 Population count as % of mean for 2013 123% 62% 99% 112% 105%

Figure 1.11. The Sumburgh Head Common Guillemot population index (black, 1978 = 100) based on five counts in June at eight study plots, the number of regularly attended sites in the breeding success plot (green), and the mean number of adults present per 100 regularly attended sites (blue) and per 100 breeding pairs (red) on the dates and times of the population counts, 2000-2013.

20 1.5. Common Guillemot Uria aalge: Breeding success at Burravoe, Yell

This was monitored (by MM) in the same plot as in 2012 (Table 1.16). Because viewing distance from the closest safe vantage point (200 m) meant the presence of an egg was more difficult to confirm than at Sumburgh Head, 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. 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 1.14, b), or where adults were only ever recorded as standing upright on two or more dates (Table 1.14, 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 ascertain their probable age.

Although a median laying date cannot be calculated, laying was about a week later than in 2012, and a lower percentage of site-holding pairs were assumed to have laid. Visits were, on average, three days apart. Given that 24% of first eggs and 38% of relay eggs in the Sumburgh Head plot did not survive for more than three days, an unknown proportion of laying at Burravoe may have gone undetected, although the adult Guillemots at Burravoe seemed more settled than at Sumburgh, egg losses through fighting may have been less, and no mass panic events were seen.

Chicks were seen at a lower proportion of laying sites (40%) than in 2012 (54%) but their survival to assumed fledging was high, with only three known to have been lost; on 8th August three adults were still present, with chicks aged at least 15, 18 and 23 days, and these were all assumed to have fledged. Of nine chick feeds noted, eight were of sandeels (two medium, six large) and one was a medium ‘sillock’ (juvenile Saithe).

Although breeding success at Burravoe was lower than in 2012, it was probably higher than in any section of the Sumburgh Head colony. It has become apparent that the small Guillemot colony at Burravoe does not attract predatory gulls, which are present throughout the breeding season at Sumburgh Head and add to the nervousness of adult Guillemots, as well as taking their eggs and chicks.

Table 1.16. Details of Common Guillemot breeding success monitoring at Burravoe in 2012-13. 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.

2012 2013 Date range visited 8/5 – 27/7 2/5 – 8/8 Checks (mean interval) 26 (3.2 days) 30 (3.4 days) Date first egg seen / assumed incubation 8/5 16/5 ST 2+ checks, assumed laid (a) 115 75 ST 1 check only from first egg to 30/6 (b) 11 17 Other regularly attended sites (c) 3 38 % laid (a/a+b+c) 89.1% 57.7% Sites where chicks were seen 62 30 Date first assumed fledged 30/6 – 2/7 8 - 11/7 Number assumed fledged (d) 59 27 Success (d/a) 0.51 0.36 Success (d/a+b) 0.47 0.29

21 1.6. Razorbill Alca torda: Population counts

At Sumburgh Head, and as with Guillemots, there were low numbers present in the monitoring plots on 4th June (50) but the other four counts were rather similar (83, 77, 86, 87; Table 1.17). The plot counts would suggest little change in numbers since 2007, after a 70% decline from 2000 (Figure 1.12), while single counts of the whole colony have been of around 200 birds in most years from 2007 (Table 1.18). Numbers were never large at the other three colonies, the highest mean counts being 34 birds in 1982 at Troswick Ness, 84 at Esha Ness in 2000, and 17 at Burravoe in 1999, but very few were present in June 2013.

Table 1.17. Mean counts of individual Razorbills in study plots at four Shetland colonies, 2012 and 2013. Statistics given are: number of counts, range, mean, standard deviation, coefficient of variation, percentage change since 2012, and population indices (1978 = 100).

Colony Unit Year n Range Mean SD CV % ch. Index Sumburgh Birds 2012 5 46-86 64.4 14.29 0.22 22.2 Head 2013 5 50-87 76.6 15.37 0.20 +18.9 26.5

Troswick Birds 2012 5 1-9 3.6 3.44 0.95 17.1 Ness 2013 5 1-4 2.2 1.10 0.50 -38.9 10.5

Esha Ness Birds 2012 5 6-18 12.2 5.12 0.42 16.8 2013 5 1-9 4.8 2.86 0.60 -60.7 6.6

Burravoe Birds 2012 5 6-11 9.0 1.87 0.21 75.0 2013 5 6-9 7.8 1.30 0.17 -13.3 65.0

Figure 1.12. Annual index (1978 = 100) of Razorbill numbers at Sumburgh Head and Esha Ness, 1976- 2013, and the mean of indices at these two colonies plus Troswick Ness and Burravoe.

Table 1.18. 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 to be not visible from the cliff top.

2001 6/6/07 18/6/08 16/6/09 8/6/10 19/6/11 11/6/12 10/6/13 626 199 197 192 133 204 189 151

22 1.6. Razorbill Alca torda: Breeding success at Sumburgh Head

This was monitored (by MM) at Sumburgh Head for the third successive year, using the marked photographs from 2011-12 and adding on any 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 or more 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 the Head and it would be spurious to clump them into ‘plots’.

Despite the uncertainties inherent in the methodology (no egg or chick was ever seen at 42% of sites at which pairs were assumed to have laid), it was evident that Razorbill breeding performance in 2013 was intermediate between that in 2011 and 2012. The proportion of attended sites at which pairs laid was relatively low and fewer chicks were seen than in 2012. The three cases of chick loss were all in the first week of July, and all chicks known to have been alive on 7th July, or hatched after this were assumed to have fledged. Unattended eggs were noted at two sites, on 18th May and 30th June. At the former, the pair relaid and fledged a chick, at the latter incubation resumed and a chick also fledged. Only one chick feed was noted, a small ‘sillock’ (juvenile Saithe) on 14th July.

Table 1.19. The number, status and outcome of Razorbill breeding sites monitored at Sumburgh Head, 2011-13. 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 Date range visited 4/5 – 11/7 3/5 – 26/7 3/5 – 6/8 Checks (mean interval) 22 (3.2 days) 42 (2.0 days) 41 (2.4 days) First egg seen / assumed incubation 4/5 3/5 8/5 ST 2+ checks, no egg or chick seen (a) 13 10 18 Egg / chick seen (b) 34 44 25 ST 1 check only from first egg to 30/6 (c) 10 5 15 Other attended sites (d) 6 7 14 % laid (a+b/a+b+c+d) 74.6% 81.8% 59.7% Sites where chicks were seen 7 38 13 Date first assumed fledged None 27-28/6 16/7 Number assumed fledged (e) 0 30 10 Success (e/a+b) 0.00 0.56 0.23 Success (e/a+b+c) 0.00 0.51 0.17

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

Monitoring logistics and constraints Counts of adults attending colonies are made from land in the first hours of daylight from late March to early May along 13 coastal stretches (Table 2.1). Mu Ness and Dale to Wats Ness are contiguous stretches of coast, as are West Burra and Kettla Ness, and these have usually been counted on the same mornings; in both cases the sections are separated by gaps of unsuitable habitat. East Foula (surveyed by Sheila Gear) is split into two sections that have sometimes been counted on different mornings. Lunning and Levaneap are also contiguous, but separated by a large gap between colonies and are often surveyed on different mornings.

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 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 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, and priority for second counts is given to coastal stretches where the first count was suspected to have been low for those reasons.

The 2013 counts The single count at Ronas Voe (10th April) was higher than two unusually low counts in 2012 (80, 71) but still below those in 2010-11, while the count at Hillswick Ness (13th April) was also slightly lower than those made in good conditions in 2009-12; both were made in good conditions, with the few birds ashore flushing easily (Table 2.1; Figure 2.1). At Wats Ness to Dale, and at Mu Ness (13th April), tide flooding against an onshore breeze made birds hard to see at the former, and birds were flying offshore before the latter section could be completed; both counts were low for these reasons and the long-term data are not plotted. The respective counts at West Burra and Kettla Ness were of 142 and 82 (8th April), and 129 and 115 (12th April), which was unusual in that when two counts have been made previously, numbers have been either slightly higher or lower than the first count in both sections; both counts were in good conditions, with birds flushed easily. The possibility that some individuals were displaying in groups at West Burra on 8th and then at Kettla Ness on 12th cannot be discounted, and it might be appropriate to treat these sections as a single unit, rather than plotting the higher counts for each section (Figure 2.2), in which case the total of 244 on 12th was 12.5% lower than the single count in 2012 (Figure 2.3).

Table 2.1. Pre-breeding counts of adult Black Guillemots at colonies, 2004-13. 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 2012.

West Coast 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 % change Ronas Voe 112 [101] 114 [117] [112] 101 [137] 131 80 [101] +26.3 % Hillswick Ness 212 214 [238] [233] 266 [286] [293] [249*] [284] [260] -8.5 % Mu Ness [122] [114] [110] 124 [127] [91*] [136] [103*] -24.3 % Wats Ness-Dale [154] [147] [163] 172 [209] [173*] [215] [182*] -15.3 % West Burra 113 [130] [134] 120 133 152 [144] [157] 142 -9.6 % Kettla Ness 83 [91] [96] 86 102 118 [114] [122] 115 -5.7 % East Foula 134 143 112 125 119 147 167 157 184 166 -9.8 % West Total 955 955 954 1028 1140 1059 1178 1069 -9.3 %

East Coast 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 % change Lunning 73 68 57 63 [64] [67] 72 84 [68] [88] +29.4 % Levaneap 266 240 241 [224] [271] 268 270 [271] 246 -9.2 % Kirkabister 147 132 148 140 [164] [170] 169 181 174 179 +2.9 % Aithsetter 82 [86] 93 99 [95] [100] 112 125 114 116 +1.8 % Mousa 134 [108] [115] [99] 137 [158] [194] 182 [176] Boddam-Virkie 123 [102] 116 117 [121] [120] 136 132 [131] -0.8 % East Total 825 736 770 755 887 935 978 935 Overall Total 1691 1725 1696 2027 2037 2113

24 Figure 2.1. Counts of adult Black Guillemots in northwest Mainland, at Hillswick Ness (black dots) and Ronas Voe (open circles), 1983-2013.

Figure 2.2. Counts of adult Black Guillemots at West Burra (black dots) and Kettla Ness (open circles), 1983-2013.

Figure 2.3. Counts of adult Black Guillemots at West Burra and Kettla Ness combined, 1983-2013. When two counts were made, the lower is also shown (open circles: markers for the higher and lower counts overlap completely in 1989 and 2007-09). Counts were all on the same mornings except for those in 1983, 1987, 1999 and 2000 (the higher).

Figure 2.4. Counts of adult Black Guillemots at east Foula, 1982 and 1996-2013.

25 Along the east coast of Foula, despite an offshore breeze, choppy conditions in the southern section on the first count (13th April, 166 birds) and a heavy swell on the second (29th April, 115) meant a third count was made (4th May, 140) but this was also affected by heavy swell; although lower than in 2012, the first count was still markedly higher than those in 2001-09 (Figure 2.4).

In northeast Mainland, the single count at Lunning (5th April) was similar to that in 2011; much of the cliff in this section is ‘blind’ from the land, and it was suspected that some birds ashore were overlooked on the single count in 2012 (Figure 2.5). At Levaneap, both counts (246 on 5th April, 244 on 26th April) were in good conditions but were around 10% lower than a rather consistent set of counts in 2009-12. Although one section of cliff at Kirkabister is completely ‘blind’ and one can never be sure that a few birds ashore have not been overlooked, the two counts of 179 birds in 2013 (3rd April, 26th April) and those in 2011-12 suggest numbers are currently 15-20% higher than in 2002-07.

Figure 2.5. Counts of adult Black Guillemots in northeast Mainland, at Levaneap (black dots), Kirkabister (grey dots), and Lunning (open circles), 1982-2013.

In southeast Mainland, numbers at Aithsetter (110 on 1st April, 116 on 7th April) remain higher than in the late 1990s and early 2000s, while the single count along the coast between Boddam and Virkie (1st April) also suggests numbers are also currently relatively high, but still below the two counts of 163 and 156 in 1989 (Figure 2.6). The decrease between 1989 and 1991 on this section was attributed to a crude oil pollution incident in March 1991, when 22 Black Guillemots were found oiled on beaches in the area. Unfortunately, no count of Mousa was made this year.

Figure 2.6. Counts of adult Black Guillemots in southeast Mainland, at Boddam to Virkie (black dots) and at Aithsetter (open circles), 1982-2013.

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

The block of moorland between Sullom Voe and St Magnus Bay has been surveyed for breeding Red- throated Divers every other year, once at the end of May or in early June, and again at the end of June or in early July to detect late nesting attempts. This year, these first two checks were made slightly later, to take account of later laying in recent breeding seasons, and a third (or more) visit was made from late July onwards to assess breeding success. Part of the study area is also monitored by Natural Research Projects Ltd, and we co-operated closely with their contract staff (Mark Chapman and Simon Hulka) to limit any disturbance by reducing the number of visits to the minimum necessary, and sharing results. First checks were made during 11-16th June, the second visits on 5th and 10th July, and the third and any subsequent visits from 31st July onwards.

Breeding was proved on 26 lochs or pools, but this figure cannot be directly compared with previous years because of the extra visits made in 2013 (Table 3.1). The first two visits in 2013 detected 21 breeding pairs, six lochs with only an empty nest scape, and nine lochs with only adults present; excluded from the latter (and Table 3.1) was a second non-breeding pair on a large loch where a breeding pair laid but failed. Thus, two visits still detected the highest number of known breeding pairs (21) and lochs with diver activity (36) since the early 1980s. Six broods of one chick and two broods of two were judged to have fledged (mean brood size at fledging of 1.25), although the latter included one semi-runt chick that was still present at the end of September, several weeks after its sibling was presumed to have fledged. Breeding success was therefore low, at 0.38 fledged per breeding pair. Of the 18 pairs known to have failed, seven were known or believed to have hatched chicks that did not survive (either small chicks were seen or eggshell fragments were found in empty nests).

Table 3.1. Red-throated Diver breeding activity on lochs in the Northmavine study area, 1981-2013.

Year 1981 1982 1983 1989 1990 1991 1992 1993 1994 Breeding proved 27 28 27 14 16 10 10 7 7 Empty nest scrape only 4 3 8 2 3 6 5 8 8 Total lochs with nests 31 31 35 16 19 16 15 15 15 Divers present, no nest found 3 3 5 9 11 2 7 4 15 Total lochs with diver activity 34 34 40 25 30 18 22 19 30

Year 1996 1998 2001 2003 2005 2007 2009 2011 2013 Breeding proved 11 7 16 7 16 11 16 15 26 Empty nest scrape only 6 1 0 4 1 4 3 6 4 Total lochs with nests 17 8 16 11 17 15 19 21 30 Divers present, no nest found 2 8 7 10 9 9 16 9 11 Total lochs with diver activity 19 16 23 21 26 25 35 30 41

27 4. Moulting Common Eiders Somateria mollissima in Yell Sound and Sullom Voe

A full census of the moulting Eider population of Shetland was completed in August 2012, when a total of 4,627 birds were counted, 20% fewer than in 2009. The next full census is scheduled for August 2015, and in the intervening years surveys from land will be carried out of southern Yell Sound, where moulting birds have become attracted to aquaculture sites, and of Sullom Voe which held a small moulting flock until the late 1990s.

The southern Yell Sound voes were surveyed on 7th August, in a SW 3 light breeze and calm seas; the 494 Eiders found were all in the Dales Voe and Colla Firth area. There were 14 female/juveniles at the beach at the head of Colla Firth. A flock close to the salmon cages at the mouth of Colla Firth was initially estimated at c.130 birds, but then swam into the mouth of Dales Voe where an accurate count of 142 was made (c.50% adult males). Most of these spent time feeding in open water away from mussel lines, but the flock then swam further into Dales Voe where 85 males and 231 females were feeding at mussel lines near the head of the voe, with some roosting ashore. There were also 22 female/juveniles in the Houb of Fora Ness.

On 21st August, Eiders in Sullom Voe were counted from the shore during the monthly beached bird survey. Wind direction was NE 2 and observation range was excellent. The total of 118 birds comprised: 3 males at Jetty 2; 2 females and two juveniles in Garths Voe; 3 females with broods of 1, 1, 2 in the Houb of Scatsta; 62 males and 10 females off Scatsta Ness; 3 females and 1 juvenile off Otter Loch; 1 female with 3 juveniles in The Houb; 13 female/juveniles along the SW shore of Fugla Ness; 8 males and 3 female/juveniles west of Ungam. In addition, there were two females with broods of 2 and 3 in Gluss Voe. The Sullom Voe total of 118 Eiders compares with counts of 72 in 2012, four in 2009 and none in 2006.

Clearly, as well as utilising new locations at aquaculture sites in southern Yell Sound, Eiders have returned to the former moulting location of Sullom Voe; the distance between the two areas is too great for Eiders to swim regularly when flightless, so they can be regarded as discrete moulting locations. On the basis of the 2012 census total, and allowing for a small number of birds that are usually present at Little Holm in northern Yell Sound, around 13% of the Shetland population was present in Yell Sound and Sullom Voe in late summer 2013.

Table 4.1. Counts of moulting Common Eiders in Yell Sound and Sullom Voe, 2005-13 (nc = no count).

Area 2005 2006 2009 2010 2011 2012 2013 Northern Yell Sound nc 0 3 nc nc 12 nc Sullom Voe 11 0 4 nc nc 72 118 Southern Yell Sound 190 109 666 771 386 499 494 Total 201 109 673 771 386 583 612

28 5. Winter counts of diving seabirds and seaduck

5.1. Sullom Voe and southern Yell Sound

On 23rd January (three observers), a light southeast breeze quickly dropped to mostly glass calm, giving perfect conditions with extreme visibility. Most freshwater was frozen, and good numbers of Goldeneye were present in Sullom Voe, with more Red-breasted Mergansers there than in 2011/12 (Table 5.1). In Yell Sound, there were few Long-tailed Ducks (38) at the main feeding area off the Lunna coast, but 26 in the Wick of Copister, Yell. Few Great Northern Divers were seen, despite the perfect sea conditions. The count of Slavonian Grebes in Sullom Voe was not as high as in most recent winters, but four were present in the Orka Voe area (Table 5.2). The count of Black Guillemots in Sullom Voe was particularly high, and the calm conditions and good light also contributed to a high count in Yell Sound.

Table 5.1. Counts of diving seabirds and seaduck in Sullom Voe, 2005-13.

Sullom Voe 2005 2006 2007 2008 2009 2010 2012 2013 Date 15/2 18/11 22/2 19/1 15/11 27/12 10/12 12/2 21/12 16/1 23/1 Common Eider 3 2 0 0 0 2 0 2 0 2 0 Long-tailed Duck 2 1 0 2 2 1 0 0 0 1 1 Common Scoter 0 0 0 0 0 1 0 0 0 0 0 Velvet Scoter 0 0 0 1 0 0 0 0 1 0 0 Goldeneye 20 7 22 12 17 14 3 49 39 33 47 Red-breasted Merganser 53 50 28 39 72 65 131 121 194 74 124 Goosander 0 0 0 0 0 0 0 0 0 0 1 Red-throated Diver 0 1 1 0 4 2 4 0 0 1 2 Black-throated Diver 0 0 0 0 0 0 0 0 0 0 1 Great Northern Diver 1 1 0 0 7 6 2 1 5 2 3 Slavonian Grebe 13 6 7 9 19 26 25 31 18 29 21 Cormorant 22 2 7 7 20 7 27 7 62 5 18 Shag 133 55 68 182 219 145 420 119 732 87 90 Common Guillemot 5 1 9 0 0 0 0 0 0 1 0 Razorbill 4 6 4 9 2 1 0 0 0 1 2 Black Guillemot 106 30 76 83 49 59 68 49 145 121 195 Little Auk 0 0 0 8 1 0 0 0 0 1 0 Puffin 0 0 0 1 0 0 0 0 0 0 0 Total 362 162 222 353 414 329 680 379 1208 358 505

Table 5.2. Counts of diving seabirds and seaduck around the southern Yell Sound islands, 2005-13. Count conditions: ** = moderate to good, *** = good or excellent throughout.

Southern Yell Sound 2005 2006 2007 2008 2009 2010 2012 2013 Date 15/2 18/11 22/2 19/1 15/11 27/12 10/12 12/2 21/12 16/1 23/1 Count conditions *** ** *** *** *** *** *** *** ** *** *** Common Eider 80 121 46 54 35 68 12 70 19 55 27 Long-tailed Duck 91 97 169 138 100 164 105 47 46 80 98 Common Scoter 0 0 0 1 1 0 0 0 0 0 0 Goldeneye 17 6 4 12 6 0 1 6 28 18 8 Red-breasted Merganser 1 3 6 1 1 12 17 8 0 13 13 Red-throated Diver 1 3 4 4 8 10 5 0 3 3 2 Great Northern Diver 4 3 2 2 8 9 2 2 2 5 3 Slavonian Grebe 0 0 0 0 0 0 0 0 5 3 6 Cormorant 108 136 40 54 464 335 322 361 484 104 353 Shag 558 790 612 520 1065 886 1444 1038 575 513 691 Common Guillemot 17 59 21 9 12 36 1 2 3 1 1 Razorbill 0 0 4 2 3 13 1 0 1 0 0 Black Guillemot 356 286 454 284 520 638 602 281 362 325 580 Little Auk 0 1 0 2 1 11 5 0 0 1 0 Puffin 0 0 0 2 0 0 0 0 0 0 4 Total 1233 1505 1360 1085 2224 2182 2517 1815 1582 1121 1786

29 5.2. Hascosay, Bluemull and Colgrave Sounds, and South Unst

South Unst has been included in the standard Hascosay, Bluemull and Colgrave Sound (HBC) route on all surveys since 2001/02, except on a late count in moderate to poor conditions on 18th March 2003, and totals given are for the area as a whole (Table 5.3). A survey on 8th February (three observers) was in perfect conditions throughout. Numbers of Common Eiders wintering in this area have increased greatly since 2001, and the 1,458 counted represented 30% of the Shetland population estimate (August 2012). On this survey, 95% of birds were in three flocks: 39 at salmon cages in Sand Wick, Yell, 275 in Linga Sound, and 1,073 in northern Hascosay Sound; these last two flocks were feeding at ‘natural’ seabed sites.

The count of Long-tailed Ducks was the highest since 1992/93, but was complicated by the fact that during the survey many were flying between the freshwater Loch of Belmont on Unst, and Uyea Sound. Brydon Thomason had seen 500-600 on the loch in the morning and fortunately was able to check that there were only c.50 there (not included in the total in Table 5.3) at the same time (14.00 h) as we watched birds flying in to feed at the Uyea Sound salmon cages, and counted 387 there. We saw very few at the other traditional feeding areas, in Hascosay Sound (11), between Hascosay and Linga (67), south of Sound Gruney (5), and in the South Wick of Hascosay (1). Large flocks of Long-tailed Ducks have been displaying on the Loch of Belmont in spring since 2006, but how long they have been using the loch in mid winter (and therefore potentially overlooked on boat surveys) is unclear.

Of the 18 Great Northern Divers recorded, eight were along the HBC route and ten were off south Unst. The large increase in numbers of Cormorants wintering in the area in the 2000s has been sustained; the average of 11 counts during the 1990s was only 16 birds (range 1-57). As in recent winters, pelagic auks were virtually absent on this survey, but the perfectly calm sea and good light will have contributed to the high count of Black Guillemots.

Table 5.3. Counts of diving seabirds and seaduck in Hascosay, Bluemull and Colgrave Sounds, and off South Unst, 2001-13. Count conditions: ** = moderate to good, *** = good or excellent throughout.

Hascosay, Bluemull and 2001 2004 2005 2006 2007 2009 2012 2013 Colgrave Sounds 10/12 14/2 6/3 27/1 18/2 2/12 23/12 22/1 8/2 Count Conditions *** *** ** *** *** *** *** ** *** Common Eider 208 839 999 1001 1159 1241 1084 978 1458 King Eider 0 1 1 0 0 0 0 0 0 Long-tailed Duck 230 262 313 200 161 144 317 365 555 Common Scoter 0 0 0 2 1 0 3 1 2 Velvet Scoter 0 2 2 0 0 0 0 0 0 Goldeneye 23 9 9 14 4 7 25 11 12 Red-breasted Merganser 7 11 2 8 15 17 13 36 26 Red-throated Diver 7 10 7 5 51 12 16 20 21 Great Northern Diver 27 6 7 1 9 23 17 9 18 White-billed Diver 0 0 0 0 1 0 0 0 1 Cormorant 19 88 80 116 263 96 90 252 243 Shag 1471 915 295 871 1243 1496 569 554 804 Common Guillemot 44 6 3 47 10 3 2 2 6 Razorbill 0 0 0 0 2 0 0 0 1 Black Guillemot 724 436 294 541 359 367 506 277 885 Puffin 0 1 0 0 0 0 0 1 0 Total 2760 2586 2012 2806 3278 3406 2642 2506 4032

30 5.3. Pool of Virkie to Bay of Quendale

The area was surveyed from land on 9th February. Weather conditions were perfect, but the remains of a moderate to heavy westerly swell affected the outer Bay of Quendale, although excellent light compensated for this somewhat (Table 5.4). Few Common Eiders were seen, but the count of Long-tailed Ducks was considered accurate (the species can be difficult to count accurately if birds are feeding). The relatively high count of 34 Great Northern Divers in Bay of Quendale (two were in full wing moult) may have been due to birds that normally feed further offshore having sought shelter from the swell in the lee of Garths Ness; eight were in the West Voe of Sumburgh and one was off Grutness. Many Common Guillemots were ashore at Sumburgh Head and most of those counted were on the sea close to the breeding cliffs.

Table 5.4. Winter counts of diving seabirds and seaduck between Pool of Virkie and Bay of Quendale, 2005-13. Count conditions: ** = moderate to good, *** = excellent throughout.

Pool of Virkie to 2005 2006 2008 2009 2010 2011 2013 Bay of Quendale 27/2 6/12 2/2 12/1 19/2 13/12 10/2 30/12 9/2 Count conditions *** *** *** ** *** ** *** ** ** Common Eider 49 25 24 45 59 23 43 21 9 Long-tailed Duck 100 45 57 201 93 152 121 242 114 Common Scoter 0 0 0 0 0 1 0 7 1 Goldeneye 2 4 5 32 38 7 15 38 12 Red-breasted Merganser 0 2 0 0 1 0 0 1 0 Red-throated Diver 2 12 11 10 0 10 1 10 5 Black-throated Diver 1 0 0 0 0 0 0 0 0 Great Northern Diver 22 27 22 18 27 15 30 24 43 Cormorant 2 8 0 0 3 6 2 1 2 Shag 83 503 77 76 102 418 115 119 139 Common Guillemot 0 3 6 2 0 1 4 26 79 Razorbill 0 4 2 1 2 0 0 2 2 Black Guillemot 36 26 21 34 24 4 61 29 71 Little Auk 0 0 0 0 0 0 0 1 0 Total 297 659 225 419 349 637 392 521 477

31 5.4. Burra, Trondra, and the Scalloway Islands

The area was surveyed (three observers) on 24th January. Conditions were generally excellent until heading south from Weisdale Voe through the outer Scalloway islands, when a very light south-easterly breeze freshened slightly, giving moderate to heavy ripples for the rest of the survey. The main concentrations of Common Eiders were 126 scattered around north Trondra, and a flock of 353 near the Meal baa, West Burra, while most Long-tailed Ducks (90) were in northern Clift Sound (Table 5.5). Despite most freshwater being frozen, the count of Goldeneye was unexceptional, while Red-breasted Merganser numbers around Burra and Trondra were more similar to those in 2008 and 2010 than the high count in January 2012. Slavonian Grebes were found in Clift Sound (6), Burland, Trondra (1), the Bur Wick area (9), and around Flotta and Greena (4), in Weisdale Voe. Few pelagic auks were seen, while the rippled sea and lowering light conditions probably reduced the count of Black Guillemots among the Scalloway Islands. The area can be difficult to cover completely within the daylight constraints of midwinter, and the sea area off the entrances to Sand Voe and Seli Voe were omitted on the 2012 and 2013 surveys; however, this area is more or less covered by counts from land usually undertaken by the Shetland Biological Records Centre.

Table 5.5. Counts of diving seabirds and seaduck around Burra, Trondra and the Scalloway Islands, 2005- 13. Count conditions: ** = moderate to good, *** = excellent throughout. The 2012 survey did not cover the west coast of West Burra, or around South Havra. Birds seen in the entrances to Sand and Seli Voes in 2005-10 (not covered in 2012-13) are listed in a footnote.

Burra / Trondra / Havra Scalloway Islands / Weisdale Voe Year 2005 2006 2008 2010 2012 2013 2005 2006 2008 2010 2012 2013 Date 22/2 26/1 14/2 8/1 27/1 24/1 22/2 26/1 14/2 8/1 27/1 24/1 Count conditions *** *** *** *** *** ** ** *** *** *** *** ** Tufted Duck 0 0 0 22 0 11 0 0 0 1 0 0 Common Eider 465 542 565 615 367 576 215 164 307 182 173 94 Long-tailed Duck 121 100 126 109 113 103 20 20 13 8 12 18 Common Scoter 0 1 0 0 6 2 0 0 0 2 0 0 Velvet Scoter 0 0 0 1 1 1 0 0 0 0 0 0 Goldeneye 20 43 20 54 33 38 9 4 5 9 1 6 Red-br. Merganser 43 30 52 48 117 54 8 4 19 16 8 28 Goosander 0 0 0 0 0 1 0 0 0 0 0 0 Red-throated Diver 29 6 28 2 22 6 3 0 3 0 5 2 Great Northern Diver 7 12 21 2 3 7 13 15 17 22 38 24 Little Grebe 0 0 0 0 1 0 0 0 0 0 0 0 Slavonian Grebe 2 0 0 5 20 7 1 3 4 12 11 13 Cormorant 142 45 62 49 21 57 128 85 67 193 23 62 Shag 500 412 332 471 324 315 240 404 182 398 318 286 Common Guillemot 29 66 23 2 2 3 31 165 28 2 5 0 Razorbill 5 3 1 0 1 6 1 10 5 0 2 4 Black Guillemot 217 185 275 282 153 200 131 277 126 282 173 208 Little Auk 0 0 0 0 4 0 0 0 0 0 14 0 Puffin 0 0 4 0 0 0 0 0 0 0 0 2 Total 1580 1445 1509 1608 1188 1433 800 1151 776 1127 783 747

Birds seen off the entrances to Sand Voe and Seli Voe: 22nd February 2005: Common Eider 64. Long-tailed Duck 4. Slavonian Grebe 5. Cormorant 25. Shag 15. Common Guillemot 1. Black Guillemot 7. 26th January 2006: Common Eider 73. Great Northern Diver 4. Slavonian Grebe 2. Cormorant 12. Shag 44. Common Guillemot 15. Razorbill 3. Black Guillemot 21. 14th February 2008: Common Eider 142. Cormorant 1. Shag 39. Common Guillemot 4. Black Guillemot 3. 8th January 2010: Common Eider 33. Goldeneye 1. Long-tailed Duck 1. Great Northern Diver 2. Slavonian Grebe 2. Cormorant 1. Shag 35. Common Guillemot 2. Black Guillemot 26.

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6. Beached Bird Surveys

This was the 35th consecutive year of the monthly beached bird survey in Shetland, which is carried out by the authors and a team of volunteers (see Acknowledgements). Coverage includes Unst, north and east Yell, south Fetlar, west Bressay, Fair Isle, 47 beaches on Mainland, mainly on the ‘outer’ coast, as well as 15.6 km of shoreline in the northern half of Sullom Voe, and nine other beaches (totaling 5.2 km) in Yell Sound.

6.1. Incidence of oiling

The 49 oiled birds found in 2013 was the highest number since 2008, although the proportion oiled remains below the levels of the 1980s and 1990s (Table 6.1); most (63%) were found from March to May and most (59%) were Fulmars (Table 6.2). Seven of the nine found in March were on beaches south of Lerwick and Scalloway, whereas all but one of the 17 found in May were in northwest Mainland or northwest Yell (including four in northern Yell Sound, the only ones found in Yell Sound or Sullom Voe during the year).

Eleven oil samples were sent for analysis (Table 6.3). The first, from a Herring Gull found in January at Sand (west Mainland) that had been drenched in brown oil, was an unrefined crude similar to Murchison and Statfjord crudes from the northern East of Shetland Basin. The remains of another Herring Gull, two Fulmars and a Kittiwake on the same beach were also oiled with what appeared to be the same oil, and apart from a lightly oiled Herring Gull at Scousburgh (south Mainland), these were the only oiled birds found that month. A Guillemot at Fair Isle in February (the only oiled bird that month) had been oiled by a fuel oil, as had Guillemots at Sumburgh and Boddam (both south Mainland) in March (which may have had a common source), although oil on a Fulmar at nearby Channerwick was Ninian crude. On 4-5th May, a live oiled Guillemot and a Razorbill were reported from Vementry, in the south of St Magnus Bay, while further west a heavily oiled live Common Gull was seen at Melby and (most oddly) at least two Tufted Ducks on Loch of Norby were believed to have been oiled. A search of some west coast beaches on 6-7th May found only a small patch of oil on Burra and an oiled pair of Fulmar wings at Sandwick, Eshaness; both were fuel oils. Three samples taken at the end of May from different species were similar to that of the Sandwick Fulmar (and possibly the oil patch on Burra), as was that on another Fulmar at the end of July.

Four drums of waste oil were removed from beaches, at North Roe (Yell Sound) in January, St Ninians Ayre (south Mainland) in March, Scatsta Ness (Sullom Voe) in July, and Culswick (west Mainland) in August.

Table 6.1. Annual summary details for the Shetland Beached Bird Survey, 2004-13. Total figures are from March 1979 to December 2013.

Year Km. Corpses Oiled Total/km % Oiled Oiled/km. 2004 585.20 1,498 22 2.560 1.47 0.038 2005 578.80 1,370 9 2.367 0.66 0.016 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 581.12 807 49 1.389 6.07 0.084 TOTAL 20,546.62 68,263 4,695 3.322 6.88 0.229 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 1.609 4.04 0.063

33 Table 6.2. Seabirds and seaduck found on beached bird surveys in 2013. For each species the first figure is the total found, the second the number that were oiled (in bold). ‘Other species’ were: Greylag (15), Mallard (1), Grey Heron (1), Oystercatcher (14), Lapwing (2), Curlew (4), Redshank (1), Snipe (1), Woodcock (1), Wood Pigeon 1, Rock Dove (6), Short-eared Owl (1), Hooded Crow (4), Raven (3), Starling (2). *Figures for km surveyed are rounded from a figure of 48.96 km for a complete monthly survey; beaches with nesting terns are not surveyed in May, June and July.

SPECIES J F M A M J J A S O N D SUM Common Eider 0 0 0 0 3 0 1 3 0 0 0 1 8 Long-tailed Duck 0 0 0 0 0 0 0 0 0 1 0 0 1 Red-br. Merganser 0 0 0 0 0 0 1 0 0 0 0 0 1 Red-throated Diver 1 0 0 0 0 0 0 0 0 0 0 0 1 Fulmar 11/2 15 31/5 44/2 51/11 45/2 85/6 44 20/1 13 12 8 379/29 Sooty Shearwater 0 0 0 0 0 0 0 1 0 0 0 0 1 Gannet 2 1 5 9/1 12/2 3 16/1 10 6 2 3 4 73/4 Cormorant 1 0 0 0 1 1 0 1 0 0 0 1 5 Shag 1 1 1 5 9 5 4 0 1 0 1 2 30 Great Skua 0 0 0 0 1 1 3 2 0 0 0 0 7 Black-headed Gull 0 0 0 0 0 2 0 0 0 0 0 1 3 Common Gull 1 1 1 1 7/3 2 6 3 1 0 0 1 24/3 Lesser Bl.-backed Gull 0 0 0 1 0 1 2 0 1 0 0 0 5 Herring Gull 7/3 2 1 6/2 4 3 4 5 7 9 5 1 54/5 Iceland Gull 0 0 0 0 0 0 0 0 0 0 1 1 1 Glaucous Gull 1 0 0 0 0 0 0 0 0 0 0 0 1 Great Bl.-back. Gull 0 2 0 1 5 3 2 2 2 1 2 6 26 Kittiwake 2/1 0 1 1 2 3 2 2 0 0 2 0 15/1 Common Tern 0 0 0 0 0 1 1 0 0 0 0 0 2 Arctic Tern 0 0 0 0 0 0 4 1 0 0 0 0 5 Common Guillemot 4 3/1 9/4 13 37/1 21/1 15 9 7 4 1 6 129/7 Razorbill 1 0 2 2 1 0 4 0 0 0 0 0 10 Black Guillemot 0 0 0 0 2 0 2 5 1 0 0 1 11 Little Auk 0 0 0 0 0 0 0 0 0 2 0 1 3 Puffin 0 4 0 0 2 2 2 0 0 0 1 1 12

Total 32 29 51 83 138 93 154 88 45 32 28 34 807 Oiled 6 1 9 5 17 3 7 0 1 0 0 0 49 Km. surveyed* 49.0 49.0 49.0 49.0 48.0 45.0 47.6 49.0 49.0 49.0 49.0 49.0 581.12 Corpses / km. 0.65 0.59 1.04 1.69 2.88 2.07 3.24 1.80 0.92 0.65 0.57 0.69 1.389 % Oiled 18.8 3.4 17.6 6.0 12.3 3.2 4.5 0 2.2 0 0 0 6.07 Oiled / km. 0.12 0.02 0.18 0.10 0.35 0.07 0.15 0 0.02 0 0 0 0.084 Oiled after death 1 0 1 0 0 0 0 0 0 0 0 0 2 Net/rope/hook tangled 0 0 0 1 1 0 2 1 0 0 0 0 5 Other species 5 3 3 1 11 4 10 10 5 4 0 2 58

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Table 6.3. Results of analyses by Fugro (ERT Scotland) Ltd of oil samples collected in 2013. S = slightly oiled (< 10%), M = moderately oiled (10-30%), H = heavily oiled (> 30%). *, ** indicates similarity and probable common source.

No. Date Location Sample Type Possible type/source 221 28/1 Sand, W Mainland Herring Gull Crude Similar to Murchison and Statfjord, most 100% oiled likely to have originated from production fields in the northern East of Shetland Basin 222 24/2 North Haven, Fair Isle Guillemot M Fuel Accidental release or illegal bilge discharge 223 25/3 Boddam, SE Mainland Guillemot H Fuel* Accidental release or illegal bilge discharge, may be related to 225 224 25/3 Channerwick, SE Mainland Fulmar S Crude Positive match to Ninian, accidental release during terminal/tanker operations, or from a process upset (i.e. discharge water treatment) 225 28/3 Sumburgh, S Mainland Guillemot H, Fuel* Accidental release or illegal bilge discharge, fresh may be related to 223 226 7/5 Sands of Meal, Burra Patch of soft, Fuel Accidental release or illegal bilge discharge black oil 227 6/5 Sandwick, NW Mainland Fulmar M Fuel** Accidental release or illegal bilge discharge 228 21/5 Braewick, NW Mainland Guillemot M Fuel** Accidental release or illegal bilge discharge 229 21/5 Tangwick, NW Mainland Fulmar S Fuel** Accidental release or illegal bilge discharge 230 21/5 Burravoe, NE Mainland Gannet M Fuel** Accidental release or illegal bilge discharge 231 23/7 Urafirth, NW Mainland Fulmar M Fuel** Accidental release or illegal bilge discharge

35 6.2. Non-oiled mortality

For the eighth successive winter, very few Guillemots (22: six oiled) were found on the October 2012 to March 2013 surveys (Figure 6.1). This is probably a reflection of the low numbers spending time in Shetland inshore waters during recent winters, with relatively few having been seen on recent winter surveys by boat (Tables 5.1-5.4). Few Razorbills (three) or Puffins (three adults, one first-winter, all February) were also found on the October to March 2012/13 surveys, and there was no indication that the wreck of Puffins that occurred in eastern Britain in March 2013 extended as far north as Shetland.

Unusually, the largest monthly number of dead Guillemots was in May (Table 6.4). Many of these (and most of those found in June) were adults in summer plumage and with no white tips to their greater underwing coverts (white tips are a feature of first-year birds). Those found intact and freshly dead were emaciated, perhaps an indication of the poor condition of some adults early in the breeding season. Relatively high numbers of adult Guillemots were also found in summer 2004 (Figure 6.2), another year of extremely low breeding success, while large numbers of adult and first-year birds had been found during January to April 1996. Some apparent adults in full summer plumage had broad white fringes to their greater underwing coverts (Table 6.4), and whether this occurs normally in a proportion of adults, or is a feature of immature birds is uncertain. Unlike 2012, few first-winter Guillemots were found in early autumn.

Figure 6.1. The number of Common Guillemots (per km; black = oiled) found on the Shetland beached bird survey each winter (October to March), 1979/80 to 2012/3.

Figure 6.2. The number of unoiled Guillemot corpses found on May, June and July beached bird surveys, 1979-2013. See Table 6.4 for explanation of age categories.

36 Table 6.4. Age composition of Common Guillemots found on the 2013 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. Those in April – June with white fringes were in summer plumage and older than first-year birds. 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 2 67 3 100 9 100 9 75 22 59 13 68 White fringes 0 0 0 0 0 0 1 8 6 16 2 11 White tips 1 33 0 0 0 0 2 17 9 24 4 21 Unaged 1 0 0 1 0 2 Total 4 3 9 13 37 21 Month July August September October November December Guillemot No. % No. % No. % No. % No. % No. % No white tips 9 75 7 78 5 71 0 0 0 0 5 83 White fringes 2 17 1 11 0 0 0 0 0 0 0 0 White tips 1 8 1 11 2 29 4 100 1 100 1 17 Unaged 3 0 0 0 0 0 Total 15 9 7 4 1 6

In most years there is a seasonal peak in Shag mortality in late winter and early spring, but the scale of this varies considerably between years and very few were found in 2013 (Figure 6.3).

Figure 6.3. The number of unoiled Shags found (per 10 km) on the January to April beached bird surveys, 1980-2013.

37 7. 2013 Publications and Presentations

Bao, R., Bartolome, C., Barros, A., Camphuysen, C. J., De Souza, J. A., Fortin, M., Heubeck, M., Maside, X. & Sandoval, A. 2013. Status, genetic diversity and possible breeding origin of wintering Great Northern Divers Gavia immer in Galicia, northwest Spain. Oral presentation by MH at International Loon and Diver Workshop, Tvarminne Zoological Station, Hanko, Finland, 21-22 September 2013. Heubeck, M. 2013. Censusing and monitoring breeding seabirds in Britain and Ireland. British Birds 106: 306-324. Heubeck, M. & Mellor, R. M. 2013. Recent changes in the status and distribution of moulting Common Eiders Somateria mollissima in Shetland. Seabird 26: 71-86.

8. Acknowledgements

Gary Bell and Roger Riddington assisted with winter seabird surveys; thanks also to boatmen George Lamont Williamson (Challenge) and Jonathan Wills (Dunter III). The following participated in the beached bird survey during 2013: Gary Bell, Juan Brown, Andy Cook, Martha Devine, Harry Edwards, Dick Foyster, Andy Gear, Liz Gillard, Paul Goddard, Newton Harper, Derick Herning, Cecilia James, Helen Moncrieff, Dave Okill, David Parnaby, Mike Pennington, George Petrie, Roger Riddington, Malcolm Smith, Jonathan Swale, Brydon Thomason, Howard Towll and Glen Tyler.

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

38 Appendix 1. Seabird monitoring on Foula in 2013, conducted by the Foula Ranger Service (Sheila and Penny Gear, and Fran Dyson Sutton), summarised by Martin Heubeck.

Common Eider. A count along the east coast of Foula on 25th July recorded 165 adults, a similar number to 2012, but the low count of chicks and the high proportion of broods of one would suggest a high level of predation.

17/7/04 16/7/05 22/7/06 27/7/07 26/7/08 27/7/09 24/7/10 26/7/11 27/7/12 25/7/13 Males 94 102 82 73 94 110 48 74 108 94 Females 101 81 61 60 70 89 66 51 50 71 Adults 195 183 143 133 164 199 114 125 158 165 Chicks 48 44 37 27 25 53* 19 26 81 27 Brood/1 12 3 7 11 8 10 8 7 7 15 Brood/2 4 6 8 4 7 12 3 6 12 6 Brood/3 5 7 2 1 1 4 0 1 8 6 Brood/4 2 2 2 0 0 1 0 1 4 0 Brood/5 1 0 0 1 0 0 1 0 2 0 Total 243 227 180 160 189 252 133 151 239 192

Red-throated Diver. The number of breeding attempts was the highest in the past decade, although success was relatively low. Only two broods of two chicks were known of, and of the nine known chicks, one was found dead, four disappeared while fairly small, and four survived to presumed fledging.

Foula Red-throated Divers 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Sites occupied at least once 13 11 13 11 10 12 10 13 12 13 Breeding attempts 7-9 9 9 7 8 11 9 11 8 12 Sites where chicks hatched 4 7 7 6 6 7 5 7 6 7 Minimum number of chicks 5 11 9 7 6 10 5 9 8 9 Chicks presumed fledged 4 7 3 7 4 9 4 5 5 4 Breeding success 0.57-0.44 0.78 0.33 1.00 0.50 0.82 0.44 0.45 0.63 0.33

Northern Fulmar. Breeding success was monitored in four plots, which were checked on 31st May, 2rd and 4th June. One or two adults were present at 237 sites on at least one of these dates, and apparently occupied sites (AOS) were defined as those occupied on each of the three visits (135, 57%). Chicks were counted on 16th August, when there were 96 present, all in sites occupied on each of the three earlier visits, making average breeding success per AOS 0.73. No dead chicks were seen.

Plot No. Sites AOS Fledglings Success 3 78 45 29 0.64 4 67 25 20 0.80 6 59 44 31 0.70 8 33 21 16 0.76 Sum 237 135 96 0.71 Mean 0.73

European Shag. Few attempted to breed and the season was again late. In ten plots, only four pairs were known to have laid, and two pairs that laid late each had a single chick, both of which fledged. A count around the whole island by boat on 25th July, in fine conditions, found only 338 birds (the last full census of the island, in June 2000, recorded 2,021 nests and a further 256 were estimated).

Shag 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Well-built nests 8 7 33 25 37 46 42 28 13 8 Young fledged 0 0 35 14-21 7 55 53-54 20 6 2 Success/AON 0 0 1.06 0.50-0.75 0.19 1.20 1.23-1.26 0.71 0.46 0.25

39

Arctic Skua. Birds again returned late. The number of occupied territories (AOT, whole island) and the number of pairs laying were slightly lower than in 2012, and while adults defended territories well they were found to be underweight when caught for ringing. Eight pairs hatched chicks in early July but these did not appear to have been fed and all died within a day or two. Most birds had left the colony by mid July.

Arctic Skua 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 First seen 14/5 20/5 26/4 26/4 21/4 24/4 26/4 22/4 3/5 AOT ? 68 79 71 41 63 50 41 37 35 Pairs laid 13 18 61 42 10 49 39 32 27 26 Mean clutch ? ? 1.68 ? 1.71 1.43 1.73 1.63 1.58 1.77 Fledged 0 1 2 0 0 22 (1) 0 4 0 Success/AOT 0 0.01 0.03 0 0 0.35 0.00 0 0.11 0

Great Skua. Many birds did not return to territories until well into April or early May. Mean clutch size (1.76, n = 38) was similar to 2011 (1.74), but chick survival was poor with a number found predated. Sixteen chicks were ringed but only eight survived to fledge by 12th August, with four still too young to fly.

Plot AOT Clutch Brood Chicks Chicks size/AOT size/AOT ringed/AOT fledged/AOT 1 10 1.60 0.90 0.40 0.30 2 28 1.82 0.71 0.42 0.18

Common Gull. A total of 20 adults attended the colony at the Groups quarry, but only five pairs were seen to lay. Six chicks survived to fledge successfully and another one was killed by a Herring Gull at fledging.

Herring Gull. Seventeen adults were present at the colony at da Swaa but only four pairs were seen to lay. Only five chicks were observed and none appeared to fledge. A Herring Gull was observed taking a Fulmar chick from its nest.

Black-legged Kittiwake. Breeding numbers continue to decline; a census on 10th June recorded 327 well- built nests (378 in 2012). Breeding was very late, most attempts failed around possible hatching, and no chicks were recorded.

In under da Stee 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Completed nests 108 106 118 91 13 70 52 50 44 32 Fledged 0 27 26 1 0 23 3 0 0 0 Success 0 0.25 0.22 0.01 0 0.33 0.06 0 0 0 Hodden 2008 2009 2010 2011 2012 2013 Completed nests 2 46 31 22 20 18 Fledged 0 22 0 2 0 0 Success 0 0.48 0 0.09 0 0 Mean success 0 0.41 0.03 0.05 0 0

Arctic Tern. Arctic Terns again returned a week later than usual. Five were seen off the Voe on 15th May and 20 were seen on the Clettins (below Veedal) on 17th May. Although up to 50 birds were observed at the south end of the island, through to the end of May and the beginning of June, none attempted to breed there. The small colony on the Clettins increased to c.50 birds and a number laid, but only one chick survived to fledge. A few adults remained until the end of August.

Common Guillemot. Guillemots returned late and numbers appeared low. Very few chicks were seen and they were very late, with some still on the ledges on 2nd August.

40

Razorbill. Razorbill numbers appear to be in decline. On 16th June most pairs in the plots that used to be monitored appeared to have failed.

Atlantic Puffin. Puffins were late back, with very few onshore before mid May. Numbers remained low throughout the summer, until the last week of July when good numbers of non-breeders arrived and stayed until mid August. Breeding birds were bringing in small numbers of larval whitefish, but it is not known if any chicks survived to fledge.

41