Kleptoparasitic interactions by bald eagles (Haliaeetus leucocephalus) during marine mammal foraging events

Abstract

Stealing of food items from another animal, or kleptoparasitism, has been well studied in bird species. Bald eagles are known kleptoparasites of other birds and occasionally other species, however kleptoparasitic interactions with mammals are relatively uncommon. We describe instances of bald eagles taking, or attempting to take, fish and mammal prey from three species of cetaceans (bottlenose dolphins (Tursiops truncatus), harbour porpoises (Phocoena phocoena vomerina) and killer whales (Orcinus orca)) and one species of pinniped (harbour seal (Phoca vitulina richardii)) on the east and west coast of the United States of America. We discuss possible drivers of this emerging behaviour, including bald eagle population increases, reductions in other prey abundance, and changes in prey choice (for harbour porpoises). Further research is needed to determine if this behaviour is opportunistic in nature, or a more common foraging strategy.