Species with similar ecological requirements that overlap in range tend to segregate their niches to minimize competition for resources. However, the niche segregation possibilities for centrally foraging predators that breed on isolated Subantarctic islands may be reduced by spatial constraints and limitations in the availability of alternative prey. In this study we examined spatial and trophic aspects of the foraging niches of two sympatrically breeding penguin species, macaroni (Eudyptes chrysolophus; MAC) and chinstrap (Pygoscelis antarcticus; CHIN) penguins, at Bouvetøya over two breeding seasons. To measure at-sea movements and diving behaviour, 90 MACs and 49 CHINs were equipped with GPS loggers and dive recorders during two austral summer breeding seasons (2014/15 and 2017/18). In addition, blood samples from tracked birds were analysed for stable isotopes to obtain dietary information. CHINs displayed marked interannual variation in foraging behaviour, diving deeper, utilizing a larger foraging area and displaying enriched values of δ¹⁵N in 2014/15 compared to the 2017/18 breeding season. In contrast, MACs dove to similar depths and showed similar δ¹⁵N values, while consistently utilizing larger foraging areas compared to CHINs. We suggest that low krill abundances in the waters around Bouvetøya during the 2014/15 season resulted in CHINs shifting toward a diet that increased their niche overlap with MACs. Our findings may partly explain the decreasing number of breeding CHINs at the world’s most remote island, Bouvetøya, while also highlighting the importance of characterizing niche overlap of species using multi-season data sets.

具有相似生态要求但范围重叠的物种倾向于隔离它们的生态位以尽量减少对资源的竞争。然而，在孤立的亚南极岛屿上繁殖的中央觅食捕食者的生态位隔离可能性可能会因空间限制和替代猎物可用性的限制而降低。在这项研究中，我们检查了两种同域繁殖的企鹅物种通心粉 ( Eudyptes chrysolophus ; MAC) 和颊带 ( Pygoscelis antarcticus )觅食生态位的空间和营养方面。; CHIN) 企鹅，在布韦托亚进行了两个繁殖季节。为了测量海上运动和潜水行为，在两个南方夏季繁殖季节（2014/15 和 2017/18）期间，90 个 MAC 和 49 个 CHIN 配备了 GPS 记录器和潜水记录器。此外，对来自被跟踪鸟类的血液样本进行了稳定同位素分析，以获得饮食信息。与 2017/18 繁殖季节相比，CHIN 在觅食行为方面表现出显着的年际变化，潜水更深，利用更大的觅食区域，并在 2014/15 年显示出丰富的 δ ^{15 N 值。}相比之下，MAC 潜入相似的深度并显示出相似的 δ ¹⁵N 值，同时与 CHIN 相比，始终使用更大的觅食区域。我们认为，2014/15 季节期间 Bouvetøya 附近水域的磷虾丰度较低，导致 CHIN 转向饮食，增加了它们与 MAC 的生态位重叠。我们的研究结果可能部分解释了世界上最偏远岛屿布韦岛繁殖 CHIN 数量的减少，同时也强调了使用多季节数据集表征物种生态位重叠的重要性。