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Isle of May seabird studies in 2004

Harris, M. P.; Wanless, S.; Murray, S.; Mackley, E.. 2005 Isle of May seabird studies in 2004. Peterborough, JNCC, 28pp. (JNCC Report 375)

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Abstract/Summary

The 2004 breeding season was the least successful ever recorded for most seabirds on the Isle of May. Adult return rates of all the species followed were normal or above average, indicating that survival was generally high. European shags, black-legged kittiwakes and common guillemots all bred late. Most species appeared to find conditions difficult, with colony attendance being low. Problems were exacerbated by strong winds and prolonged heavy rain in late June, which resulted in the deaths of large numbers of young of shags and puffins. Although lesser sandeels remained the main food of young puffins and kittiwakes, guillemots and razorbills fed their young mainly clupeids and shags brought in a wide variety of bottom-living fish. Northern fulmar breeding success (0.21 chicks per incubating pair) was the lowest recorded. European shags bred late and had a very unproductive season (0.25 chicks fledged per pair laying compared with 1.83 in 2003). Many chicks died in torrential rain in late June but evidence from regurgitations and pellets suggest that adults also had problems finding food. Survival over winter appeared to have been normal, with a return rate of 82.2%. Black-legged kittiwakes bred extremely late. The low success (0.27 chicks fledged per active nest) reversed the improvement noted in recent years. Many chicks died after fledging, further decreasing the strength of the 2004 year class. Adult return rate (81.8%) was normal. Common guillemots started breeding about 7-10 days later than normal. Both egg and chick losses were substantially higher than normal and productivity, at 0.51 chicks leaving per pair laying, was the lowest recorded on the Isle of May. Many chicks were left unattended but most probably died rather than being killed by gulls. Adults fed their chicks almost entirely on sprats. Chicks grew slowly and all the evidence suggested that feeding conditions were poor. Adult return rate (90.1%) was higher than in recent years. Razorbill breeding success (0.54 chicks per pair) was well below the long-term average. Adult return rate (84.3%) was higher than the long-term average. For the first time since monitoring started, small clupeids, rather than sandeels, were the main item in the diet of chicks. Atlantic puffin breeding success (0.60 chicks per pair) was one of the lowest ever recorded on the Isle of May. In part this was due to burrows being flooded during the severe weather in late June but chicks also grew slowly, suggesting that feeding conditions were bad. Adult return rate (87.9%) was high, indicating that over-winter survival had been high. There has been no commercial sandeel fishery on the Wee Bankie since 2000. Studies on the Isle of May in 2000-2003 generally reported an increase in breeding success in some species (notably shag and kittiwake), thus providing circumstantial evidence that closure of the fishery could potentially have an immediate and positive effect on seabird productivity. However, the situation was radically different in 2004 with all species having very low breeding success. 2004 was also characterised by sandeels, particularly the 1+ age class, being largely absent from the diet of many seabirds. While the reason for these changes is currently unknown, the possibility that they reflect major changes in the North Sea ecosystem due to climate change is a strong candidate.

Item Type: Publication - Report (UNSPECIFIED)
Programmes: CEH Programmes pre-2009 publications > Biodiversity
CEH Sections: _ Biodiversity & Population Processes
Funders/Sponsors: Joint Nature Conservation Committee
Additional Keywords: Isle of May, Seabirds
NORA Subject Terms: Zoology
Date made live: 09 Mar 2009 16:11
URI: http://nora.nerc.ac.uk/id/eprint/6602

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