The foraging areas used by adult Sooty Terns Onychoprion fuscatus during incubation and early chick-rearing on Bird Island, Seychelles, were investigated using small GPS loggers. Birds departed the colony mainly during the night and foraged by day. Most foraging trips were completed within 24 hr, but during incubation the longest duration recorded was seven days and 14 hr (during which the bird travelled 2,783 km and reached a maximum of 692 km from the colony). Departures were generally in an arc from south (180°) through westerly to 40°. Sooty Terns foraged frequently in waters over the Seychelles Bank shelf break, but some birds travelled further, including to the area around the Coco-de-Mer Ridge ca. 400 km north of Bird Island. In the four days after hatching, adult foraging trips tended to be shorter, within 24 hr, and the small sample of tracks obtained revealed that they potentially foraged over deeper areas. Most of the foraging areas identified were within the Seychelles’ Exclusive Economic Zone, with some foraging areas occurring outside the Seychelles marine protected area.
Neumann et al. (Wed,) studied this question.