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

South Polar Skuas Stercorarius maccormicki prey mainly on other birds when occupying areas allopatrically. However, in areas where they live sympatrically with the Brown Skua S. antarcticus fish appears to dominate their diet probably because of the monopolization of the terrestrial resources by the latter. Twenty eight stomach samples of South Polar Skuas were collected throughout the breeding season at Half Moon Island, South Shetland Islands, Antarctica. Fish were the most frequent prey (100 %) and also predominated in mass (98%); their importance remained constant throughout the study period. Although a colony of Chinstrap Penguin Pygoscelis antarctica is located nearby and that the number of Brown Skuas was very small, the South Polar Skuas did not prey on the penguins. The result suggests that fish, at least in certain regions, can constitute a selected food resource even when terrestrial resources are not limited. Thus, competitive exclusion alone does not explain the feeding ecology of South Polar Skuas.