Oceanographic habitats of two sympatric North Pacific albatrosses during the breeding season

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.

Temporal increase in organic mercury in an endangered pelagic seabird assessed by century-old museum specimens

“…Therefore, we sampled a single central breast contour feather from all remaining individuals. Because black-footed albatrosses range widely throughout the Pacific Ocean while foraging within a lifetime (39,46,47), we did not expect differences in collection locality to confound signals of temporal variation in bioavailable Hg exposure. We similarly sampled central breast feathers for Hg analysis from russet-crowned motmots and Altamira orioles.…”

Prey consumption and energy transfer by marine birds in the Gulf of Alaska

“…This pattern is not surprising given that shelf regions are usually more productive than adjacent regions of deep ocean. Among the species foraging over the basin are albatrosses, which export energy to islands to the southwest of the study area (Hyrenbach et al, 2002), and stormpetrels that may export small amounts of energy to the coastal zone where they nest. Hunt et al (2000) ARTICLE IN PRESS found that the Gulf of Alaska PICES region had the highest densities of seabirds in any of the PICES regions for which data were available.…”

Seasonal sexual segregation in twoThalassarchealbatross species: competitive exclusion, reproductive role specialization or foraging niche divergence?

“…Detection of such macrohabitat selection is not straightforward, however, as overall foraging ranges of males and females may overlap considerably, and even if there are apparent differences in core areas (e.g. Hyrenbach et al 2002), these could conceivably result from a combination of individual preferences unrelated to gender, given the small sample sizes.…”