Daily energy expenditure of great cormorants Phalacrocorax carbo sinensis wintering at Lake Chiemsee, Southern Germany

In the winters of 1993/94 and 1994/95 the daily energy expenditure (DEE) of Great Cormorants Phalacrocorax carbo sinensis was measured using the doubly labelled water technique (DLW). This was the first time the method has been used on a Phalacrocoracid species. DLW trials were carried out on 5 caged birds and on 5 free-ranging wild birds at Lake Chiemsee. The mean body mass of the captive birds (2079 g) was not significantly different from and that of wild birds (2122 g). There was no significant difference in the total body water (TBW) of the two Cormorant groups (55.9% in captive birds and 56.7% in free-ranging birds). Estimated DEE (+/- SD) averaged 1325 +/- 130 kJ day(-1) (n = 5) in the caged birds and 2094 +/- 174 kJ day(-1) (n = 5) in the free-ranging ones, a highly signficant difference. To match their DEE, it was calculated that the Cormorants had to consume 341 g of fish per day under aviary conditions and 539 g in the wild.