Abstract
<title>Abstract</title> <p> Wilson’s Storm-Petrels ( <italic>Oceanites oceanicus</italic> ) are among the most abundant and widely distributed seabirds in the world, yet their migration patterns have remained largely unknown due to the lack of direct tracking data. We deployed 50 light-level geolocators on breeding adults at a colony on King George Island in Antarctica and retrieved data from 16, providing the first complete annual cycle tracking of the austral storm-petrel (family Oceanitidae) breeding in the Southern Hemisphere. Given the cosmopolitan distribution, we expected divergent migration trajectories among individuals, potentially heading towards both the Pacific and the Atlantic Oceans. However, all tracked individuals undertook trans-equatorial migrations exclusively to the North Atlantic, travelling 36,213 ± 2,788 km annually on average. The Gulf of Maine was the primary non-breeding area, and the Río de la Plata region was a major staging site, especially during northward migration. These findings indicate that this Antarctic breeding population maintains high spatial consistency in their use of these key areas and follows a clearly patterned, partially clockwise loop migration across the Atlantic Ocean. Despite the species’ large population size and broad distribution, such site-specific use of non-breeding habitats at the population level suggests greater vulnerability to environmental changes than its current conservation status implies. </p>