Information on marine predator at-sea distributions is a key component of spatial management frameworks that aim to identify regions important for conservation. Tracking data from seabirds have been widely used to define priority areas for conservation, but such data are often restricted to the breeding population. This also applies to penguins in Antarctica, where identification of important habitat for nonbreeders has received limited attention. The foraging ranges of breeding penguins are constrained to near-shore areas by the high energy needs of chicks at the colony. Conversely, nonbreeding adults are expected to have larger foraging distributions, which may increase their conspecific interactions with birds from neighboring colonies and their vulnerability to threats distant from the breeding colony. Here, we study the movement behavior of nonbreeding Adélie penguins tracked during the 2016/17 breeding season at King George Island (Isla 25 de Mayo) in the South Shetland Islands, Antarctica. We quantify how nonbreeding penguins’ moment behavior varies in relation to environmental conditions and assess the extent of spatial overlap in the foraging ranges of nonbreeders and breeders, which were tracked over several years. The utilization distributions of breeders and nonbreeders overlapped in the central Bransfield Strait. Habitat segregation was greater during the crèche stage of the breeding season compared to incubation and brood, because chick provisioning still constrained the foraging range of breeders while nonbreeders commenced pre-molt foraging trips into the Weddell Sea. Nonbreeders increased their prey search and area-restricted foraging behavior in areas where sea surface temperatures were lower, sea-ice concentration were higher, and over shallower bathymetry nearer the coastline of the Antarctic Peninsula. Differences in the at-sea spatial distribution of nonbreeding and breeding penguins highlight the need to account for different life-history stages when characterizing habitat use of marine predator populations. This is particularly important for “sentinel” species monitored as part of marine conservation and ecosystem-based fisheries management strategies.
Dr Chris Oosthuizen (South Africa)
Dr Azwianewi Makhado (South Africa)