The importance of fish in the diet of the South Polar Skua (Stercorarius maccormicki) at the South Shetland Islands, Antarctica

MONTALTI D.; CASAUX R.; CORIA N.; SOAVE G.; GRAÑA GRILLI M.

EMU

CSIRO PUBLISHING

Año: 2009 vol. 109 p. 305 - 309

0158-4197

Where South Polar Skuas (Stercorarius maccormicki) occur in the absence of Brown Skua (S. antarcticus), theirmain prey consists of other birds. In contrast, where the two species occur together, fish appears to dominate the diet ofSouth Polar Skuas, probably because Brown Skuas monopolise the terrestrial resources. Twenty-eight stomach samplesof South Polar Skuas were collected throughout the breeding season at Half Moon Island, South Shetland Islands,Antarctica. Fish were the most dominant prey item (100% frequency, 98% prey mass); their importance remainedconstant throughout the study period. Although there is a colony of Chinstrap Penguin (Pygoscelis antarctica) nearbythe South Polar Skua population and there are very few Brown Skuas, the South Polar Skuas did not eat penguins. The resultsuggests fish are selected preferentially over terrestrial resources, at least in certain regions, and particularly whenavailability of terrestrial resources is limited. Thus, competitive exclusion by Brown Skuas may not fully explaindietary choice of South Polar Skuas.