The Food of Young Razorbills on the Isle of May and a Comparison with That of Young Guillemots and Puffins

Abstract

Sandeels were the staple food of young Razorbills which were fed, on average, 2.9 times d-1. The calculated mean feed weights (and calorific values) for 1982, 1983 and 1984 were 8.5 g (61 kJ), 7.2 g (52 kJ) and 6.3 g (43 kJ), respectively. Young aged 3-11 d received the most feeds. Puffin chicks received 4-5 feeds d-1 of a number of smaller sandeels, herring and a range of other species, while young Guillemots received 3-4 feeds of a single large sandeel or sprat. There was virtually complete overlap of the chick rearing periods and a marked similarity in the diets of chicks in the three species. The greatest dietary overlap was between Razorbill and Puffin. Razorbill chicks received far less food than other young and the species had a relatively low breeding success. Food and breeding performance should be monitored carefully.