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Isle of May seabird studies in 2002

Wilson, L. J.; Wanless, S.; Harris, M. P.; Russell, D.. 2003 Isle of May seabird studies in 2002. Peterborough, JNCC, 29pp. (JNCC Report 338)

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Abstract/Summary

During the 2002 season, weather conditions on the Isle of May were poor, with much more rain than usual, and strong westerly and easterly winds. Common guillemots, razorbills, Atlantic puffins and black-legged kittiwakes experienced lower breeding success relative to the long-term average, although common guillemots and razorbills did better than in 2001. In contrast, northern fulmars had their best season since 1995, and European shags had their best season ever. Timing of breeding for all species was normal, although European shags and black-legged kittiwakes started breeding earlier than in 2001. Return rates for razorbills and Atlantic puffins were close to the long-term average, whereas those for common guillemots and black-legged kittiwakes were around 6% lower. European shag return rates, in contrast, were much higher than the long-term average. Lesser sandeels Ammodytes marinus were the predominant prey items for all species except common guillemots, which mainly brought back clupeids for their chicks. Northern fulmars had a relatively productive season, with breeding success estimated at 0.48 chicks per incubating pair. This is above the long-term average and the highest success since 1995. European shags had an extremely productive breeding season. Breeding started earlier than in 2001 and overall breeding success (1.66 chicks per incubated nest) was the highest recorded since intensive monitoring began in 1986. Black-legged kittiwakes started breeding earlier than in 2001, but conditions appeared less than favourable at the start of the season and losses were high during incubation. Breeding success (0.47 chicks per pair laying) was much lower than in 2001, and below the long-term average. Common guillemot productivity in 2002 (0.68 young per pair laying) was the third lowest value recorded since monitoring began in 1986 and continued the trend of declining breeding success noted in recent years. Some chicks were temporarily neglected, but fledging weights were close to the long-term average. Razorbill breeding success (0.65 chicks per pair laying) was slightly lower than the long-term average, but higher than that in 2001. Most losses occurred during incubation, while survival of hatched chicks to fledging was very high. Breeding success of Atlantic puffins (0.72 chicks per pair laying) was lower than in 2001 and was slightly below the long-term average. The return rate of adult colour-ringed European shags in 2002 (92.2%) was the highest since 1998. Black-legged kittiwake return rates (73.5%) were much lower than in 2001, and lower than the long-term average. The return rate of common guillemots (87.0%) was slightly below the long-term average whereas razorbill return rates (83.8%) were slightly higher than the long-term average. The return rate of Atlantic puffins (83.5%), although much lower than in 2001, was similar to the long-term average. Lesser sandeels predominated in the diet of European shags, black-legged kittiwakes, razorbills and Atlantic puffins in 2002. As in 2001, well over half of common guillemot chick diet was made up of clupeids. As in 2000 and 2001, there was no commercial sandeel fishery on the Wee Bankie during 2002. Studies on the Isle of May in 2000 and 2001 provided circumstantial evidence that the closure of the fishery could potentially have an immediate and positive effect on seabird productivity. In particular, breeding success of European shags bounced back to record levels and black-legged kittiwake breeding success returned to the higher levels typical of the pre-fishery period. In 2002, breeding success of the European shag, an inshore forager which relies almost completely on older sandeels, was the highest on record and continues the upward trend, post-fishery closure. Black-legged kittiwakes however, which also heavily rely on sandeels, but which target the youngest age-class and forage offshore, experienced relatively low breeding success and did not maintain the improved performance shown in 2000, immediately after the fishery closure. For Atlantic puffins, the trend of increasing breeding success over the previous four years was not maintained, although it was similar to the 2000 value. Common guillemots and razorbills, which are less reliant on sandeels, continued the recent trend of having low breeding success relative to the long-term average, although both species were more productive than in 2001. Northern fulmars, for which sandeels appear not to be an important prey item, experienced breeding success above the long-term average, continuing the apparent year to year fluctuations. It was uncertain in 2000 whether environmental factors, e.g. hydrographic conditions, that potentially affect the growth and life history strategy of sandeels, were involved in the recovery of the breeding success of European shags and black-legged kittiwakes. A new EU-funded interdisciplinary project was started in 2001 and continued during 2002 to try to investigate this further.

Item Type: Publication - Report (UNSPECIFIED)
Programmes: CEH Programmes pre-2009 publications > Biodiversity
CEH Sections: _ Population & Conservation Ecology
Funders/Sponsors: Joint Nature Conservation Committee
Additional Keywords: Isle of May, Seabirds
NORA Subject Terms: Zoology
Date made live: 09 Mar 2009 16:01
URI: http://nora.nerc.ac.uk/id/eprint/6599

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