Summary of the 2009 seabird breeding season on the Isle of May

After a series of very poor breeding seasons for seabirds on the Isle of May NNR, it was especially pleasing to see species doing markedly better in 2009, and overall the season was the most successful in recent years. Of the six species studied intensively, European shag had its highest productivity on record with only razorbill having productivity below average. All other species studied had their most productive season for at least four years.  Return rates were much higher than the previous two seasons for all species with only black-legged kittiwake below the long-term average. 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, however 0 group appeared in large numbers and were substantially longer than in recent years. No snake pipefish were noted in the seabird diet having been conspicuous in the previous four years.

  • Northern fulmar breeding success (0.44 chicks per incubating pair) was a large increase on the previous two years and slightly above average.

  • European shags had the most successful season on record (2.02 chicks per pair), eclipsing the previous record set last year. Return rate was high at 89.6%, well above average and the highest for six years. As in the previous three years, the food was unusually varied with sandeels making up 51.6% by mass of the diet.  Examination of sandeel otoliths indicated that 91% were from the 0 group age class.

 
  • Black-legged kittiwakes had a good season with productivity (0.70 chicks per incubated nest) the highest since 2005 and well above the long-term average.  Adult return rate (71.3%) was an improvement after two very poor years but was still below the long-term average.  The proportion of sandeel in the diet (89% by biomass) was the highest since 2005.  
  • Guillemots had a successful breeding season (0.75 chicks leaving per pair) compared to recent years.  Return rate of adults (92.0%) was normal following the low levels of the two previous winters.  Adults fed their chicks mainly on sprats (67% by number) with sandeels (28%) the main alternative.
  • Razorbill breeding success (0.61 chicks leaving per pair) was below the long-term average.  Adult return rate (97.3%) was the highest ever recorded on the Isle of May. Chick diet was almost entirely 0 group sandeels.

Atlantic puffins had a successful season with 0.72 chicks fledging per pair laying. The return rate for adults (84.7%) was normal following the poor showing over the two previous winters. Chicks were mainly fed 0 group sandeels (91% by number, 92% by biomass) that were substantially longer than during the last decade.