ANALYSIS OF THE STOMACH CONTENT OF THE BLUE-EYED SHAG PHALACROCORAX ATRICEPS BRANSFIELDENSIS AT NELSON ISLAND, SOUTH SHETLAND ISLANDS

Stomach contents of 40 specimens of the blue-eyed shag Phalacrocorax n x atriceps bransfieldensis were sampled at Nelson Island, South Shetla nd Islands, in January 1994. The analysis of the diet showed that fish were by far the main component, followed by octopods, polychaetes and gammarids, Notothenia coriiceps predominated in frequency (58%) and i n weight (65%), whereas Nototheniops nudifrons was the most important species by number (47%). The comparison with data published on pellet analysis of shags from the same colony gave similar results. However, although the methodology used in the present study requires more time in the field; it reduces the errors that arise from the examination of regurgitated casts, such as those due to erosion by digestion or loss of the otoliths through the gastrointestinal tract. The observation o f 8 nests filmed continuously during 24 h showed that the members of t he pairs alternate foraging and make 3-5 foraging trips per individual per day. The activity started as 0700 hours and finished at 2200 hour s, and the mean duration of the trips was 73 min.