2014 SOTEAG Seabird Report
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SOTEAG ORNITHOLOGICAL MONITORING PROGRAMME 2014 SUMMARY REPORT Martin Heubeck and Mick Mellor, Aberdeen Institute of Coastal Science and Management, University of Aberdeen. January 2015 CONTENTS Page 2014 Executive Summary 2 1. Monitoring of cliff-breeding seabirds 1.1. Weather 4 1.2a. Northern Fulmar Fulmarus glacialis: Population counts 5 1.2b. Northern Fulmar Fulmarus glacialis: Breeding success 6 1.3a. European Shag Phalacrocorax aristotelis: Population counts 8 1.3b. European Shag Phalacrocorax aristotelis: Breeding success 10 1.4a. Black-legged Kittiwake Rissa tridactyla: Population counts 12 1.4b. Black-legged Kittiwake Rissa tridactyla: Breeding success 13 1.5a. Common Guillemot Uria aalge: Population counts 16 1.5b. Common Guillemot Uria aalge: Breeding success and chick diet at Sumburgh Head 18 1.5c. Common Guillemot Uria aalge: Breeding success at Burravoe, Yell 23 1.6a. Razorbill Alca torda: Population counts 24 1.6b. Razorbill Alca torda: Breeding success at Sumburgh Head 25 2. Pre-breeding counts of Black Guillemots Cepphus grylle 26 3. Moulting Common Eiders Somateria mollissima in Yell Sound and Sullom Voe 29 4. Winter counts of seaduck and diving seabirds 4.1. Yell Sound and Sullom Voe 30 4.2. Hascosay, Bluemull and Colgrave Sounds (HBC), and South Unst 33 4.3. Rova Head to Kirkabister, East Mainland 34 4.4. Bressay Sound and North Bressay 35 4.5. Whiteness Voe to Skelda Voe, West Mainland 36 4.6. Vaila Sound and Gruting Voe, West Mainland 37 5. Beached Bird Surveys 5.1. Incidence of oiling 38 5.2. Non-oiled mortality 40 6. 2014 Publications and Presentations 43 7. Acknowledgements 43 Appendix. Seabird monitoring on Foula in 2014 44 1 2014 Executive Summary 1. Monitoring of cliff-breeding seabirds Northern Fulmar Fulmarus glacialis. There was a 10% increase since 2013 in apparently occupied sites at Troswick Ness, but little change at the three other colonies monitored (Sumburgh Head, Esha Ness, Burravoe). Breeding success at these colonies was slightly lower than in 2013, but still relatively high. European Shag Phalacrocorax aristotelis. There was a reversal of the non-breeding prevalent in southeast Mainland in 2011-13. Counts of nests at Sumburgh Head and between Virkie and Mousa were 69% higher than in 2013, but still 52% lower than in 2010. There were 27% fewer nests at Papa Stour than in 2006. In breeding success plots, a high percentage of nests progressed to incubation and breeding success was high (1.22 fledged per laying pair at Sumburgh, 1.56 at Burravoe). Black-legged Kittiwake Rissa tridactyla. A total of 811 nests were counted at 13 extant and former breeding stations around south Mainland, 10% more than in 2012/13 (734) but 40% fewer than in 2009/10 (1,344). A count of 361 nests at Foula was also 10% higher than in 2013 (327) and 38% lower than in 2010 (582). There were 35 nests at Papa Stour, 57% than on the last count in 2006. Breeding success at six colonies averaged 0.91 ± 0.19 SE, the highest figure since 2005 and well above the long-term average. Common Guillemot Uria aalge. The population index at four colonies was 37% higher than in 2013, probably reflecting higher colony attendance in 2014. At Sumburgh Head, median laying date was three days earlier than in 2013, hatching success of first eggs was relatively high, high colony attendance by adults aided chick survival, and breeding success at 0.54 fledged per laying pair was identical to the 1989-2013 average. Chick diet was 25% sandeels and 70% gadids, most of the latter being small Saithe. At Burravoe, hatching success and chick survival were high, and breeding success was 0.61 per laying pair. Razorbill Alca torda. A 43% increase in the population index probably reflected low colony attendance in 2013; the total number of birds counted in plots at four colonies (112) was 70% lower than in 2000 (381). At Sumburgh Head, breeding success (0.52) was markedly higher than in 2013 (0.23). 2. Pre-breeding counts of Black Guillemots Cepphus grylle A total of 1,604 adults were counted along nine sections of coast, 10% fewer than in 2012/13 (1,791). Numbers were lower at eight of the nine sections, and at many individual colonies, and it was felt that a genuine reduction in the adult population had occurred, albeit slight. Beached bird survey data suggested that mortality in the January and February gales was higher than average for recent winters. 3. Moulting Common Eiders Somateria mollissima in Yell Sound and Sullom Voe Counts from land and sea on 20-21st August located 210 birds, 151 at aquaculture sites in southern Yell Sound and 59 in Sullom Voe, markedly fewer than the totals of 612 in 2013 and 583 in 2012. 4. Winter counts of seaduck and diving seabirds Complete coverage by boat on 9-10th January of the inshore waters of Yell Sound and Sullom Voe recorded 3,794 seaduck and diving seabirds, including 94 Common Eider, 106 Long-tailed Duck, 282 Red-breasted Mergansers, 25 Great Northern Divers, 58 Slavonian Grebes, 486 Cormorants, 1,436 Shags and 1,216 Black Guillemots. Counts were also made in February of five other standard inshore recording areas. 6. Beached Bird Surveys Eleven oiled seabirds were found (six Fulmars, singles of Gannet, Shag, Lesser Black-backed Gull, Herring Gull and Razorbill), 0.9% of the total and the lowest incidence since 2005; all were very lightly contaminated. Oil on one Fulmar and the Shag was fuel, while another Fulmar was oiled with Russian crude and the Lesser Black-backed Gull with East Shetland Basin crude. January and February were particularly stormy and the incidence of Common Guillemots in February and March was higher than in the previous eight winters. Numbers of Shags and Black Guillemots were also above average for the time of year. In summary, there was no evidence that the operation of the Sullom Voe Terminal, or its associated tanker traffic, had any detrimental impact on Shetland’s seabird populations during 2014. 2 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. Frequent changes in wind direction during April kept the sea disturbed on both the east and west coasts of Shetland, even when blowing offshore, and limited the number of second counts that could be made of Black Guillemot monitoring coastal sections. Cold, windy weather around 9-12th May coincided with the onset of Common Guillemot laying and made confirming new eggs difficult, as birds were sitting very tightly. Several spells of very heavy rain later in the month caused surprisingly few problems for the Common Guillemots, but almost certainly flooded some Razorbill nest sites. Counts in study plots were started a day earlier than usual, on 31st May, taking advantage of a calm day ahead of a forecast of strong south-easterly winds during the first few days of June. Two spells of calm weather, on 14-16th and 22-23rd June, allowed five days of Zodiac work counting Shags and Kittiwakes. July was a particularly foggy month, which caused no apparent problems for breeding seabirds but hampered checks of the breeding success plots on a number of days. The most extreme weather event of the summer was torrential rain throughout 9th August. This had been well-forecast and the Shag success plots at Sumburgh Head were checked on 8th and again on 10th August; amazingly, no chicks were missing or dead on 10th and the only change was that three nests marked as incubating on 8th had become empty/trace on 10th. In summary, weather events appeared to have had little impact on seabird breeding success in 2014. 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 2014. Sumburgh Head Observer: Martin Heubeck Date Time (BST) Wind Sea state Cloud cover 31st May 2014 1300-1500 SW 1-2 Calm 6/8 5th June 2014 1300-1500 ENE 4 Moderate swell 2/8 7th June 2014 1300-1500 L&V 1-2 Calm 2-3/8 9th June 2014 1300-1500 SSE 3 Slight swell 2/8, very warm 13th June 2014 1300-1450 NE 1 Calm 8/8 Troswick Ness Observer: Martin Heubeck Date Time (BST) Wind Sea state Cloud cover 31st May 2014 1000-1145 Calm Calm 8/8 5th June 2014 1000-1115 ENE 4 Moderate swell 6/8 7th June 2014 1000-1125 E 1 Calm 8/8, very low cloud 9th June 2014 1000-1130 SSE 3 Slight swell 1/8 11th June 2014 1000-1120 SW 4 Moderate swell 7/8 Esha Ness Observer: Mick Mellor Date Time (BST) Wind Sea state Cloud cover 31st May 2014 1300-1400 SW 1 Slight swell 8/8 3rd June 2014 1230-1330 SE 5 Moderate swell 8/8 6th June 2014 1315-1415 NW 1 Moderate swell 8/8 10th June 2014 1240-1330 ESE 4-5 Moderate swell 8/8 13th June 2014 1315-1400 NW 3 Slight swell 8/8 Burravoe, Yell Observer: Mick Mellor Date Time (BST) Wind Sea state Cloud cover 1st June 2014 1005-1045 SE 3 Calm 6/8 5th June 2014 1000-1030 NE 3 Slight swell 3/8 7th June 2014 1025-1130 Calm Calm Fog 11th June 2014 0950-1030 NW 1 Calm 8/8 13th June 2014 0950-1030 Calm Calm 8/8 3 1.2a. Northern Fulmar Fulmarus glacialis: Population counts There was little change since 2013 in the number of adults or apparently occupied sites (AOS) in study plots, except for a 9-10% increase in both at Troswick Ness, with little overlap in the 2013 and 2014 counts of both parameters (Table 1.2).