Summary of the 2007 seabird breeding season on the Isle of May

The 2007 season was an exceptionally poor one for most species on the Isle of May. Of the six species studied intensively, European shag and razorbill had an average season but common guillemot, Atlantic puffin and Northern fulmar all had the worst season on record, while black-legged kittiwakes had the worst season for nine years. Severe weather conditions played a part in the poor breeding season but difficult feeding conditions were still likely to be the main reason for such low productivity. Return rates were also at all-time lows for common guillemot, Atlantic puffin and black-legged kittiwake and well below average for shag.  Although lesser sandeels remained the main food of young Atlantic puffins, razorbills and black-legged kittiwakes, common guillemots fed their young mainly on clupeids, while European shags brought in a wide variety of bottom-living fish. Very few 1+ group sandeels were present in food samples during the chick-rearing period. 2007 continued the recent trend for an increasing proportion of snake pipefish in the diet of several of the seabirds.

• Northern fulmar breeding success (0.21 chicks per incubating pair), which, with 2004, was the joint worst season on record.
• European shags began breeding earlier than in 2006 and had a productive season. Shag was the only species for which productivity (1.07 chicks per pair) was above the long-term mean. Following high mortality during the winter, return rate at 60.8% took a drop from 2006 and was well below the long-term mean. As in the previous two years, the prey eaten was unusually varied with sandeels making up only 28.3% by mass of the diet, the lowest proportion on record. All sandeels that were recorded during chick-rearing were from older (1+ group) fish.

• Black-legged kittiwakes had a very poor breeding season with productivity (0.24 chicks per completed nest) the lowest since 1999 and well below the long term average. Adult return rate (62.9%) was the lowest on record. The proportion of sandeel in the diet (48% by biomass) was also the lowest recorded.
• Common guillemots had their poorest breeding season on record with 0.28 chicks leaving per pair laying. The last four seasons have seen the three lowest breeding successes on record. As in the previous three years, many chicks were left unattended. Surprisingly, fewer were taken by gulls than killed by other guillemots and razorbills. Return rate of adults (75.2%) was also the lowest on record. Adults fed their chicks mainly on sprats with small gadoids the main alternative. Sandeels made up only 1% of the diet by mass. Chicks grew slowly and all the evidence suggested that feeding conditions were poor.
• Razorbill breeding was earlier than last year and, in contrast to most other species, breeding success (0.63 chicks leaving per pair) was close to the long-term average. Adult return rate (80.0%) was also close to the long-term average. Chicks were fed mainly 0 group sandeels.
• Atlantic puffins had their worst ever breeding season at 0.29 chicks per pair, which is a huge drop on the previous lowest figure. Unprecedented rainfall washed out numerous burrows and those chicks which managed to survive the wet conditions showed slow growth rates and high mortality. Return rate for adults (56.9%) was also the lowest on record. Chicks were mainly fed 0 group sandeels (82% by number, 76% by biomass).