South Polar Skua Population Census

Our primary hypothesis is that South Polar skua (Stercorarius maccormicki) population abundance broadly tracks summer food availability in the southern McMurdo Sound region.

Skuas and Adélie penguins (Pygoscelis adeliae) both prey heavily on Antarctic silverfish (Plueragramma antarcticum) and krill (Euphausia crystallorophias and E. superba) and overlap in breeding space during
the summer in this region, though not entirely. If we make the assumption that physical (e.g. persistent sea-ice cover) and biological (e.g. prey abundance) conditions, in the absence of other factors, affect population dynamics and growth of both seabird species’, then similar trajectories for each population could emerge. On the other hand, in McMurdo Sound, and especially along the Victoria Land Coast, appreciable numbers of skuas nest where there are no penguins. Therefore, factors not applying to
penguins (e.g. historical human occupation) would seem to be important as well to the skuas.

Distance sampling for South polar skua (Stercorarius maccormicki) was conducted at six sites at three Adelie penguin colonies on Ross Island: Cape Bird (North, Mid and South penguin colonies), Cape Crozier (East and West penguin colonies) and Cape Royds during December 2011. Repeat counts were also conducted at Cape Bird in January 2012.