IMIS

Satellite telemetry was used to identify the foraging distributions of two congeneric species of albatrosses that nest in the tropics/subtropics. Breeding black-footed albatross (Phoebastria nigripes) and Laysan albatross (Phoebastria immutabilis) nesting in Tern Island (Northwest Hawaiian Islands) and tracked during the 1998 breeding season (January - June) performed foraging trips to continental shelves off North America. Black-footed albatross made long trips to the west coast of North America (British Columbia to California). Laysan albatross traveled primarily to the north of the Hawaiian Islands, and reached the waters of the Aleutian Islands and the Gulf of Alaska. These albatross species mixed short and long trips during the chick-rearing period (February - June), but engaged in short foraging trips during the brooding period (within 18 days after chick hatched, January - February). In 1999, the breeding success of both albatross species was depressed, with a large-scale failure for the Laysan albatross. Out of nine black-footed albatross tracked, two chicks died during this study. Out of sixteen Laysan albatross tracked, the eggs of seven birds did not hatch and eight chicks died during the tracking study. Due to this massive breeding failure, the satellite tracked birds abandoned their colony and dispersed widely across the North Pacific Ocean. Thus, the 1998 (central-place foraging) and 1999 (dispersal from colonies) tracking data should be considered separately. The 1999 data provided information on albatross movements during a year of depressed reproductive success, when many birds abandoned the colony. An understanding on the interplay between the distribution and the reproductive success of North Pacific albatrosses has important implications for assessing how oceanographic variability influences their population dynamics. We thank C. Alexander, L. Carsten, P. Fernández, F. Juola, P. Sievert, A. Viggiano and S. Wang for assistance in the field, and the U.S. Fish and Wildlife Service for logistical support. This research was funded by National Science Foundation grant DEB 9629539 to D. Anderson.