Post-fledging and winter migration of Adélie penguins (Pygoscelis adeliae) in the Mawson region of east Antarctica

Seven fledging Adélie penguin (Pygoscelis adeliae) chicks and four post-moult adults were satellite-tracked using the Argos system during the winters of 1995-97 and 1998 respectively. Six fledglings departed from Béchervaise Island near Mawson station (67°35'S, 62°49'E) during late February 1996 and 1997 and were tracked for up to five months before transmissions stopped. The seventh chick left Magnetic Island near Davis station (68°33'S, 77°54'E) in February 1995 and was tracked for 32 days. All fledglings travelled northward initially, then westward along the edge of the fast-ice or in the pack-ice. Fledglings had travelled between 536 and 1931 km to the west of their natal colonies by the time transmissions ceased. Adult Adélie penguins were tracked between March and October 1998, following completion of their annual moult at Bechérvaise Island. Instruments were factory-set to transmit intermittently for the first five months and one day in four thereafter. Adult birds travelled westward until July after which time they moved north within the expanding pack-ice into known areas of high krill concentration before returning eastward toward their breeding sites. Penguin movements over the winter months were closely related to those of sea-ice in the region. Ice motion patterns were in turn influenced by gyral oceanic current systems and wind. We propose that large gyral oceanic systems provide a means for Adélie penguins to reduce costs of transport as they travel into regions of high productivity during winter and return to their breeding colonies in spring. Locations of boundaries of oceanic gyres may thus be useful to CCAMLR in the regulation of the Antarctic krill fishery as a means of delimiting management regions.