Sex differences in diving depths and diet of Antarctic Shags at the South Shetland Islands

Sexual differences in maximum diving depths and in the composition of the d iet of the Antarctic Shag (Phalacrocorax bransfieldensis) were investigated at Harmony Point, Nelson Island, South Shetland Islands, Antarctica, durin g the 1995-1996 and 1996-1997 breeding seasons. The mean maximum diving dep th estimated by the capillary-tube depth gauge technique was 37.8 m which, when compared with other studies, reflects good food availability in shallo w waters around Harmony Point. Females dived significantly deeper than male s and also reached the maximum dive depth registered (112.6 m). The analysi s of the stomach contents recovered when the individuals with capillary-tub es returned to the nest from foraging trips indicated that males ingested a lmost exclusively large Notothenia coriiceps specimens, whereas females pre yed more intensively on smaller fish. The differences observed suggest that individuals of both sexes partitioned foraging depths and food resources.