Brown skua, fish, food resources, penguins, South Polar skua


South Polar skua (Stercorarius maccormicki) and Brown skua (Stercorarius antarcticus lonnbergi) have opportunistic feeding habits and are the dominant predators in terrestrial Polar regions. These skuas exploit a wide range of food items, including marine organisms, other birds, and even garbage. In the present study, we compare the diets of these two skua species during the breeding season, using pellets and prey remains collected within their territories. The samples were collected at six sites in Admiralty Bay, on King George Island, Antarctica. We identified eight different items, which we classified as “penguin”, “flying bird”, “skua”, “fish”, “gastropod”, “krill”, “egg” and “marine debris”. In the first breeding season (2008/2009), penguins and flying birds were the food resources more abundant for both skua species, and their diet composition was similar. In the second breeding season (2010/2011) South Polar skua exploited more fish and flying birds than Brown skua; the latter exploited more eggs and penguins. Our findings corroborate those of previous studies, demonstrating that in sympatry South Polar skua exploit more fish than Brown skua. The diet of South Polar skua also varied between breeding seasons, reflecting the opportunistic foraging behavior of these skuas. As in other studies, we recorded that skua is a food resource for both skua species, but it was more common in the diet of South Polar skua. Marine debris was recorded only in the samples of Brown skua. Birds are important food items for both skuas, although significant differences were found in the diets of these sympatric species, with shifts in the composition of the diet probably reflecting fluctuations in the abundance of prey populations, which are known to be common at Admiralty Bay, although more data will be needed to confirm this link.

Author Biographies

Ana Olívia de Almeida Reis, Universidade do Estado do Rio de Janeiro

Roberto Alcantara Gomes Institute of Biology, Graduate Program in Ecology and Evolution.

Erli Schneider Costa, Universidade Estadual do Rio Grande do Sul

Unidade Hortênsias, Mestrado Profissional em Ambiente e Sustentabilidade.

João Paulo Machado Torres, Universidade Federal do Rio de Janeiro

Carlos Chagas Filho Institute of Biophysics, Laboratory of Micropollutants.

Maria Alice dos Santos Alves, Universidade do Estado do Rio de Janeiro

Roberto Alcantara Gomes Institute of Biology, Department of Ecology.


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