Factors influencing the habitat use of sympatric albatrosses from Macquarie Island, Australia

Differences in habitat use of sympatric species are influenced by variability in functional morphology and life history trade-offs and are expected to shape species resilience to environmental change. To determine differences in year-round habitat use and gain insight into how morphological and life history traits influence foraging of an albatross community from subantarctic Macquarie Island, Australia (54.6°S, 158.9°E), we quantified the physical features associated with high residence time for 10 black-browed Thalassarche melanophris; 10 grey-headed T. chrysostoma; 15 light-mantled Phoebetria palpebrata; and 12 wandering albatrosses Diomedea exulans tracked in 1994-2009. Overlap among the 4 species was greatest close to the island during the breeding season, extending north into the Tasman Sea. Nevertheless, black-browed albatrosses ranged more locally than the other species, perhaps because they have a shorter breeding cycle and morphological traits that result in less efficient flight and greater capacity to outcompete other species for prey. Nonbreeding albatrosses showed high variability in habitat use across wide ocean expanses, but all used productive frontal regions and mesoscale eddies. Increased residence times during the breeding and nonbreeding periods were associated with moderate wind speeds for all species (excluding breeding black-browed albatrosses), indicating that birds used areas where aerodynamic performance was enhanced. Given patterns in residence time at sea, and the functional and life history adaptations of each species, we suggest that black-browed albatrosses breeding on Macquarie Island will be more vulnerable to expected future climate-driven changes to wind patterns in the Southern Ocean, and potential latitudinal shifts in the Subantarctic Front.