Abstract
BackgroundSooty (Puffinus griseus) and short-tailed (P. tenuirostris) shearwaters are abundant seabirds that range widely across global oceans. Understanding the foraging ecology of these species in the Southern Ocean is important for monitoring and ecosystem conservation and management.Methodology/Principal FindingsTracking data from sooty and short-tailed shearwaters from three regions of New Zealand and Australia were combined with at-sea observations of shearwaters in the Southern Ocean, physical oceanography, near-surface copepod distributions, pelagic trawl data, and synoptic near-surface winds. Shearwaters from all three regions foraged in the Polar Front zone, and showed particular overlap in the region around 140°E. Short-tailed shearwaters from South Australia also foraged in Antarctic waters south of the Polar Front. The spatial distribution of shearwater foraging effort in the Polar Front zone was matched by patterns in large-scale upwelling, primary production, and abundances of copepods and myctophid fish. Oceanic winds were found to be broad determinants of foraging distribution, and of the flight paths taken by the birds on long foraging trips to Antarctic waters.Conclusions/SignificanceThe shearwaters displayed foraging site fidelity and overlap of foraging habitat between species and populations that may enhance their utility as indicators of Southern Ocean ecosystems. The results highlight the importance of upwellings due to interactions of the Antarctic Circumpolar Current with large-scale bottom topography, and the corresponding localised increases in the productivity of the Polar Front ecosystem.
Highlights
Sooty (Puffinus griseus) and short-tailed shearwaters (P. tenuirostris) are abundant seabirds that range widely across global oceans [1], breeding principally in New Zealand, south-eastern Australia, and southern South America [2,3]
Of the 31 long foraging trips made by sooty shearwaters, 21 were directed to the south-eastern foraging zone, and ten to the south-west
Some myctophids, including the relatively common E. antarctica, G. braueri and K. anderssoni are rich in wax esters [58,59], which act as long-term energy reserve molecules rather than immediate energy supply [60] and they form an important component of stomach oil that is fed to chicks [61]
Summary
Sooty (Puffinus griseus) and short-tailed shearwaters (P. tenuirostris) are abundant seabirds that range widely across global oceans [1], breeding principally in New Zealand, south-eastern Australia, and southern South America [2,3]. They are of cultural and economic importance for Maori and Tasmanian aboriginal societies [4,5], important as predators within their marine ecosystems, and as engineers within their island ecosystems due to their burrowing and deposition of biological material [6,7,8]. Understanding the foraging ecology of these species in the Southern Ocean is important for monitoring and ecosystem conservation and management
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