Assimilation efficiency of adult Kittiwakes and Br�nnich's Guillemots fed Capelin and Arctic Cod

Abstract

The mean assimilation efficiencies of 10 adult Kittiwakes (Rissa tridactyla) and 10 Brunnich's Guillemots (Uria lomvia) fed on Capelin (Mallotus villosus) were 77.5% and 74.4%, respectively. When fed on Arctic Cod (Boreogadus saida) they were 83.1% and 78.2%, respectively. After correction for nitrogen retention, the assimilation efficiencies decreased to 72.2%, 70.6%, 81.2% and 74.7%, respectively. Kittiwakes and Brunnich's Guillemots seem to have the same ability to utilize the energy of the different food items. The differences in assimilation efficiencies when fed two fish species was mainly related to the fat content of the fish.