Determining food intake by great Cormorants and European shags with electronic balances

Abstract

The masses of 302 food loads delivered to the nest by 10 Great Cormorants (Phal- acrocorax carbo) and 6 European Shags (P. aristotelis) rearing chicks at the Chausey Islands, France, were assessed to an accuracy of ±10 g using automatic weighing units. We present a model based on time budget and published data that transforms these weighings into the total amount of food taken at sea. Based on this model, the daily mean fresh mass of food acquired by adults, including food brought back to their chicks, was 890 g (n = 16, SD = 361) and 800 g (n = 21, SD = 292) for adult male and female cormorants, and 478 g (n = 14, SD = 207) and 583 g (n = 13, SD = 268) for adult male and female shags.