Assessing impacts of environmental change on Arctic-breeding seabirds requires a better understanding of their year-round movement and foraging ecology. Here we examined the post-breeding movements and diving behavior of thick-billed (Uria lomvia) and common murres (U. aalge) breeding on St. Lawrence Island, northern Bering Sea, by using geolocators deployed in 2016 (n = 3, per species). During 2016–2019, we examined foraging niches and exposure to nutritional stress by using stable isotope signatures and corticosterone titers of blood and feather tissues (n = 60–96, per species). We found that thick-billed murres migrated to the Chukchi Sea in the fall and wintered in the western North Pacific, whereas common murres stayed in the eastern Bering Sea in the fall and wintered in the eastern North Pacific. Nutritional stress levels of breeding common murres were higher in 2017–2019, the period of historic low winter sea-ice extent, than in 2016. Higher nutritional stress levels of post-breeding thick-billed murres were associated with lower fall sea-ice extent in the Chukchi Sea. These results indicate that the loss of sea-ice might negatively affect murres breeding in the Pacific Arctic. Divergent migratory connectivity between the two murre species might also lead to different conservation threats both inside and outside the Arctic.

要评估环境变化对北极繁殖海鸟的影响，需要对它们全年的活动和觅食生态有更好的了解。在这里，我们研究了厚嘴鸟（Uria lomvia）和普通鼠（U. aalge）的繁殖后运动和潜水行为。），使用2016年部署的地理位置定位器在白令海北部的圣劳伦斯岛上进行繁殖（每物种n = 3）。在2016–2019年期间，我们通过使用稳定的同位素特征以及血液和羽毛组织的皮质类固醇滴度（每个物种n = 60–96）检查了觅食ni和营养应激暴露。我们发现，大嘴鲈鱼在秋季迁徙到楚科奇海，并在北太平洋西部越冬，而常见的狐狸鼠则在秋天留在白令海东部，并在北太平洋东部越冬。在历史性的冬季低海冰时期，2017-2019年繁殖普通common的营养压力水平高于2016年。繁殖后的粗嘴黑的较高营养压力水平与较低的秋季海冰程度相关在楚科奇海。这些结果表明，海冰的流失可能对太平洋北极地区的鱼体繁殖产生负面影响。两个murre物种之间不同的迁徙连通性也可能导致北极内外的不同保护威胁。