The diet of the Antarctic Shag during summer at Nelson Island, Antarctica

Analysis of 139 stomach contents of the Antarctic Shag (Phalacrocorax brans-fieldensis) collected at Nelson Island, Antarctica, showed that fish were the main component in the diet, followed by octopods, gammarids, euphausiids, and polychaetes. The fish Notothenia coriiceps predominated in frequency (56%) and in mass (49%), whereas Harpagifer antarcticus was the most important by number (58%). The sizes of N. coriiceps and H. antarcticus taken by males were significantly larger than those caught by females. This dietary difference is probably due to differential prey selection related to shags' sexual dimorphism, temporal prey availability, and/or different foraging depths/areas. Observations at nests showed that females mainly foraged in the morning, whereas males foraged in the evening. No significant differences were observed between the number of daily foraging trips made by males and females, averaging 1.7 during incubation, 2.0 in early chick-rearing, and 4.6 during the late chick-rearing period. The estimated daily food intakes were 321, 315, and 758 g for females, and 421, 582, and 1,288 g for males during incubation, early and late chick-rearing, respectively.