The foraging behavior of nonbreeding Adélie penguins in the western Antarctic Peninsula during the breeding season

Abstract

Information on marine predator at‐sea distributions is key to understanding ecosystem and community dynamics and an important component of spatial management frameworks that aim to identify regions important for conservation. Tracking data from seabirds are 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. Nonbreeding penguins are expected to have larger foraging distributions than breeding conspecifics, which may alter their interactions with physical environmental factors, conspecifics, other marine predators, and threats. We studied the movement behavior of nonbreeding Adélie penguins tracked during the 2016/2017 breeding season at King George Island in the South Shetland Islands, Antarctica. We quantify how nonbreeding penguins' horizontal 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. Nonbreeders increased their prey search and area‐restricted foraging behavior as sea surface temperature and bottom depths decreased, and in response to increasing sea ice concentration. Nonbreeders tended to transit (high directional movement) over the relatively deep Central Basin of the Bransfield Strait. The majority of foraging behavior occurred within the colder, Weddell Sea–sourced water of the Antarctic Coastal Current (incubation) and in the Weddell Sea (crèche). The utilization distributions of breeders and nonbreeders overlapped in the central Bransfield Strait. Spatial segregation was greater during the crèche stage of breeding compared to incubation and brood, because chick provisioning still constrained the foraging range of breeders to a scale of a few tens of kilometers, while nonbreeders commenced with premolt foraging trips into the Weddell Sea. Our results show that breeding and nonbreeding penguins may not be impacted similarly by local environmental variability, given that their spatial and temporal scales of foraging differ during some part of the austral summer. Our study highlights the need to account for different life history stages when characterizing foraging behavior of marine predator populations. This is particularly important for “sentinel” species monitored as part of marine conservation and ecosystem‐based management programs.

A subsurface eddy associated with a submarine canyon increases availability and delivery of simulated Antarctic krill to penguin foraging regions

“…Our residence time estimates suggest that simulated krill are retained within the foraging regions for at least 1 d. Gentoo penguins tend to complete foraging trips along the WAP within a single day during the austral summer (Kokubun et al 2010). Adélies have been observed making multi-day trips during the austral summer (Riaz et al 2021, Oosthuizen et al 2022. Around PDC, however, foraging trips of both species are nearly always less than a day (M. Cimino, M. Oliver, G. Voirol unpubl.…”

“…Simulated krill counts within our study area may illustrate why penguins might forage in certain areas. Both Adélie and gentoo penguins are capable of foraging far from their colonies, with breeding Adélies having an estimated foraging range of 10−130 km and nonbreeding individuals foraging as far as 200 km from their colonies during the breeding season (Oosthuizen et al 2022). Gentoos have been observed foraging as far as 30−70 km during the breeding season (Kokubun et al 2010, Camprasse et al 2017.…”

Sea ice concentration decline in an important Adélie penguin molt area

“…Both studies note this dependence on sea ice for molt could make populations vulnerable if sea ice declines. From the West Antarctica Peninsula, birds moved into the Weddell Sea post-breeding to molt where more reliable sea ice can be found ( 40 ). In East Antarctica, Adélie penguins spent the postbreeding period between February and April in areas of higher than average SIC, possibly due to the need for ice floes on which to molt ( 41 ).…”

Connectivity of marine predators over the Patagonian Shelf during the highly pathogenic avian influenza (HPAI) outbreak

“…However, areas of low γ t may also represent resting or haul-out (i.e. land-based resting for pinnipeds) behaviours (Riaz et al 2021, Thums et al 2022, Oosthuizen et al 2022). We defined land-associated residency behaviours as any location either over land or within 1 km of land where normalised γ t values were < 0.5.…”