Summary of the 2008 seabird breeding season on the Isle of May

The 2008 season on the Isle of May was mixed. Of the six species studied intensively, European shag had its highest productivity on record whereas northern fulmar had its worst ever season. Atlantic puffin showed a marginal improvement on the lowest productivity experienced in 2007. Common guillemot productivity was well up on the previous year but, as with razorbill, was still below average, while black-legged kittiwakes had the worst season for 10 years. Weather conditions were not exceptional so difficult feeding conditions were thought likely to be the main reason for such low productivity in most species. 

Return rates, although well below average, were slightly up for black-legged kittiwake, Atlantic puffin and European shag, while for common guillemot it was the lowest on record. 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. Comparatively few 1+ group sandeels were present in food samples during the chick-rearing period. Far fewer snake pipefish were noted in the seabird diet than in the previous three years.

• European shags began breeding earlier than in 2007 and had the most successful season on record. Shag was the only study species for which productivity (1.9 chicks per pair) was above the long term mean. Following high mortality during the winter of 2006/07, return rate increased to 70.6% but was still below the long-term mean. As in the previous two years, the food was unusually varied with sandeels making up 48% by mass of the diet. Of sandeel otoliths, 40% were from older (1 group or older) fish whereas in 2007 all had been from this age class.
• Black-legged kittiwakes had a very poor season with productivity (0.23 chicks per incubated nest) the lowest since 1999 and well below the long term average. Adult return rate (66.4%) was poor with only two other years showing lower values. The proportion of sandeel in the diet (59% by biomass) was the third lowest recorded, with high proportions of clupeid (20%) and rockling (12%) recorded.  
• Although better than in 2007, breeding success of common guillemots (0.63 chicks per pair laying) continued a worrying long-term decline. As in the previous three years, many chicks were left unattended but, surprisingly, few were taken by gulls. Return rate of adults (75.0%) was the lowest on record. Adults fed their chicks mainly on sprats (76%) with sandeels (20%) the main alternative.
• Razorbill breeding success (0.58 chicks leaving per pair) was well below the long-term average, due mainly to unusually poor chick survival. Adult return rate (69.4%) was well down on the long-term average. Chicks were fed mainly 0 group sandeels.
• The breeding success of Atlantic puffins at 0.48 fledged per pair laying was the second lowest on record. Return rate for adults (59.4%) was also the second lowest on record. This was the second year in a row of poor adult return rate, following the lowest ever in 2007. Chicks were mainly fed 0 group sandeels (63% by number, 73% by biomass).