Foraging behavior of Black-footed Albatross Phoebastria nigripes rearing chicks on the Ogasawara Islands

Abstract

Pelagic top predators that range widely over thousands of kilometres increase their turn rate and slow their movements within an area of mesoscale (<10² km). This behavior is known as "Area Restricted Search, or ARS" and is associated with aggregations of prey. Foraging range, diving behavior, and ARS were studied for nine Black-footed Albatrosses Phoebastria nigripes rearing chicks on Mukojima in the Ogasawara Islands, using GPS and time-depth data-loggers. Their prey composition was examined using regurgitations. They fed on fish, fish eggs and squid within a range of 96–427 km from the colony. They made shallow (0.6±0.2 m) dives in day-time (2.2 dives per hour of at sea time) but rarely did so at night (0.1 dives per hour of at sea time). ARS behavior was observed at the scale of 11–71 km during day- and night-time and tended to occur in locations with relatively high primary production.