Post-breeding dispersal of Adélie penguins (Pygoscelis adeliae) nesting at Signy Island, South Orkney Islands

Abstract

ARGOS satellite telemetry and Global Location Sensors (geolocators) were used to identify the moult locations and the winter foraging dispersal of Adélie penguins after they left their breeding colonies on Signy Island in the South Orkney Islands. Animals were tracked during the period December 2004 to October 2005. All birds displayed a similar pattern of migratory behaviour, remaining away from colonies for approximately 9 months, at distances of up to 2,235 km. Moult locations were within the pack ice. Mean daily travel speeds to the moult locations were significantly faster when moving through open water than through pack ice. Moult occurred during February/March within a narrow latitudinal range (65-71°S), at a mean distance of 126 km from the ice edge; the mean duration of individual moult was c. 18.6 days. After moult, penguins spent the subsequent winter months moving north or north-eastward within the expanding winter pack ice, at a mean distance of 216 km from the ice edge, and in areas with ice cover [80%. The penguins returned to the vicinity of their colony between September 26 and October 22, 2005. This dependence of Adélie penguins on sea ice habitat suggests that any further reductions in sea ice extent in the Weddell Sea region would potentially have important impacts on the population processes of this pagophilic species.

Spatial and isotopic niche partitioning during winter in chinstrap and Adélie penguins from the South Shetland Islands

“…We have tracked individuals from one small colony, but it is useful to compare their dispersal patterns with those from other studies. For example, data from Adélie penguins tracked from Marguerite Bay, along the southwestern Antarctic Peninsula, demonstrate relatively local movements constrained by the development and advection of sea ice from the Bellingshausen Sea northward along the western Antarctic Peninsula (Erdmann et al 2011); birds from the South Orkney Islands exhibited larger-scale southward movements into the Weddell Sea (Dunn et al 2011); and Adélie penguins from colonies in the Ross Sea and along East Antarctica must migrate north to the marginal ice zone and daylight during winter (Clarke et al 2003, Ballard et al 2010). Among Adélie penguins, movement patterns appear to be dictated by the location of a breeding colony relative to the advancing winter sea ice.…”

“…After the breeding season Adélie penguins typically molt and forage in concentrated pack ice (50-80%; Ballard et al 2010, Dunn et al 2011, while chinstrap penguins are generally observed north of the sea-ice edge in open water (Ainley et al 1994). Therefore, these species would be expected to track the advance and retreat of sea ice.…”

“…2C, D, 3). After the breeding season, all tagged individuals moved southeast into the NW Weddell Sea where, presumably, all individuals molted (e.g., Dunn et al 2011). Incomplete data for the month of March, due to location errors associated with the equinox (Ekstrom 2004), precluded clear interpretation of movements immediately following the molt, but by mid-April most individuals had returned as far north at 608 S (Fig.…”

“…These mid-point of each section average 15.6 6 1.1 and 14.9 6 1.3 cm from the distal tip and thus represented growth occurring 69 6 20 (CI ¼ 42-110) and 59 6 11 (CI ¼ 40-96) days following the onset of molt for Adélie and chinstrap penguins, respectively (i.e., 40-100 days following the onset of molt). Given published (Dunn et al 2011) and unpublished data on molt timing (Table B3) for Adélie and chinstrap penguins, we assume that molt initiation typically occurred on 14 February for Adélie penguins and 1 March for chinstrap penguins. Thus, the sampled feather sections reflect a time from late March to early June when penguins are migrating to and/or inhabiting their over-wintering areas.…”

“…Adélie penguins are typically observed in marginal ice zones while chinstrap penguins often are observed in open waters north of the ice edge (Ainley et al 1994). Winter tracking studies have confirmed seasonal occupancy of ice zones for Adélie penguins (Clarke et al 2003, Ballard et al 2010, Dunn et al 2011, Erdmann et al 2011 while chinstrap penguins tend to be in areas typically free of ice (Wilson et al 1998, Biuw et al 2010. Even so, the previous tracking studies have examined the winter movements of each species in isolation.…”