Seabird Abstracts

Isle of May seabird studies in 2003

Wilson LJ, Wanless S, Harris MP & Jones G (2005) JNCC Report 362, ISSN 0963-8091

During 2003, weather conditions on the Isle of May, like much of the UK, were considerably warmer and drier than in recent years. Most seabird species experienced a reasonably productive breeding season, with breeding success for all species except common guillemot and razorbill being close to, or above, the long term average. European shag productivity saw its highest value on record and continued the trend of very high breeding success seen during the previous three seasons. Black-legged kittiwakes had their second most productive season since 1990. Breeding success of both northern fulmars and Atlantic puffins was close to the long term average, and similar to 2002. Common guillemot productivity was no higher than in 2002, and was still below the long term average. Razorbill breeding success was well below the long term average and lower than that of 2002. Timing of breeding was earlier for European shags and common guillemots, but normal for northern fulmar, black-legged kittiwake, Atlantic puffin and razorbill. Return rates of colour-ringed European shags, black-legged kittiwake and Atlantic puffins were close to, or above, the long term average, while those for common guillemots and razorbills were slightly lower. As in previous years, lesser sandeels were the predominant prey species for all species, except for guillemots, which mainly brought back clupeids for their chicks. There has been no commercial sandeel fishery on the Wee Bankie since 2000. Studies on the Isle of May in 2000-2002 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 has been at record levels and black-legged kittiwake breeding success returned to something approaching the higher levels (0.82-1.38) typical of the pre-fishery period.

In 2003, 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, which also rely heavily on sandeels but which target the 0-group sandeels during chick-rearing and forage offshore, experienced increased breeding success from the previous two seasons, although not quite reaching levels of 2000, immediately after the fishery closure. Breeding success for Atlantic puffins was similar to the previous three years. 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. Northern fulmars, for which sandeels appear not to be an important prey item, experienced breeding success close to 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. An EU-funded interdisciplinary project was started in 2001 to try to investigate this further and its last field season was completed in 2003.


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