Olfactory foraging in Antarctic seabirds: a species-specific attraction to krill odors

Antarctic procellariiform seabirds are known for their well-developed sense of smell, yet few behavioral experiments have addressed how these birds use olfactory cues to forage at sea. I describe results from controlled, shipboard experiments performed in Antarctic waters near Elephant Island. Birds were presented with plain or krill-scented (Euphausia superba) vegetable oil slicks, and their behavioral responses were compared. Krill-scented vegetable oil slicks were highly attractive to some but not all procellariiform species foraging in this area (p < 0.001, G-test). Cape petrels Daption capense and southern giant petrels Macronectes g~ganteus appeared at krill-scented slicks within l rnin, whereas black-browed albatrosses Diomedea melanophris appeared within 3 min. Cape petrels D, capense showed the strongest attraction: these birds were observed as much as 5 times as frequently at krill-scented slicks as compared to unscented control slicks (p < 0.001, G-test), whde storm-petrels (Oceanites oceanicus and Fregetta tropica] and Antarctic Fulmars Fulmarus glacialoides responded in equal numbers to krill-scented and unscented slicks. When considered with respect to previously published findings, these results suggest a greater complex~ty in the significance of odors to the foraging ecology of different tube-nosed species than has commonly been assumed.