MEPS 233:283-301 (2002)  -  doi:10.3354/meps233283

ABSTRACT: We characterized the movements and oceanographic habitats of black-footed (Phoebastria nigripes) and Laysan (P. immutabilis) albatrosses during the brooding and the rearing periods of the breeding cycle. Analyses of satellite telemetry data in conjunction with remotely sensed sea surface temperature and chlorophyll concentrations revealed substantial differences in habitat use between these 2 sympatrically breeding species. During the brooding period, black-footed albatross restricted their foraging to tropical waters (>20°C), while Laysan albatross ventured into the colder waters of the Transition Domain (15 to 12°C) and the Subarctic Frontal Zone (12 to 10°C). This pelagic segregation became more apparent with the expansion of the foraging ranges later in the breeding season. During the chick-rearing period, black-footed albatross commuted to the California Current (15 to 12°C) and Laysan albatross foraged in subarctic (<12°C) and Transition Domain (15 to 12°C) waters. The foraging behavior of albatrosses was scale-dependent. Over macro-mega scales of (1000 to 3000 km) albatross dispersion was influenced by large-scale ocean productivity patterns and water mass distributions. Over smaller coarse-meso scales of (10 to 100 km) albatrosses focused their foraging activities along oceanic habitats characterized by elevated ocean productivity and prey aggregation. The foraging birds traveled more slowly in the vicinity of highly productive continental shelves (central California to Washington State, Aleutian Islands), and hydrographic fronts (Transition Domain, North Pacific Transition Zone Chlorophyll Front). Conversely, the satellite tracked albatrosses commuted rapidly over tropical and subtropical waters between these foraging areas and the breeding colony. These results highlight the significance of macro-mega scale of (1000 to 3000 km) water mass distributions and coarse-meso scale (10 to 100 km) hydrographic features to far-ranging marine predators, and underscore the need to understand how physical-biological processes sustain predictable regions of elevated ocean productivity and prey aggregation in marine systems.

KEY WORDS: Area restricted searching · Frontal systems · Habitat use · Kernel analysis · Phoebastria immutabilis · Phoebastria nigripes · Satellite telemetry · Spatial segregation