Adaptive foraging strategies of Adélie penguins in the Ross Sea Region: balancing chick feeding and body condition in changing marine environments

Abstract Breeding seabirds are required to balance between feeding their chicks and maintaining their body condition. Adélie penguins ( Pygoscelis adeliae ), a keystone species of the Antarctic ecosystem, have foraging behavioral flexibility that depends on the marine environment and own body condition. This study collected tracking data and weight measurements from 47 brooding penguins during two breeding seasons at Cape Hallett (72°19´S, 170°12´E), Ross Sea. In 2021, the breeding season with a high sea ice concentration, penguins had lower body weights during the early guarding period compared to the body weights of the penguins in 2022. Penguins performed three types of foraging trips - ice hole trips, ice edge trips, and pack ice trips—during the 2021 breeding season. However, in the season characterized by a low sea ice concentration (2022), most of the foraging trips were pack ice trips. Furthermore, penguins performed relatively shorter pack ice trips and had lower foraging efforts than they did in 2021. On the other hand, we found that penguins with higher initial weights lost more weight, where for every additional 1 kg of weight, individuals lost 360 g more during the tracking period. We suggest that penguins use selective foraging strategies to adapt to their situation. Additionally, they regulate their food intake for raising chicks based on their body condition. In summary, our findings suggest how Adélie penguins determine foraging strategies and allocating food according to the marine environment and their body condition.