Fine-scale habitat uses and activity budgets of wintering Morus bassanus (Northern Gannet) in an anthropogenic seascape

Novel uses of marine seascapes, such as development of offshore wind energy, have the potential to affect the distribution and habitat use of marine wildlife including seabirds. In order to measure and mitigate such effects, it is necessary to understand not only where individuals occur, but how they are using habitat under baseline conditions. Movements of seabirds are often under-studied during the nonbreeding period, when they are not tied to terrestrial breeding sites. We used GPS transmitters to track Morus bassanus (Northern Gannet) wintering in the New York Bight, which contains the first offshore wind energy developments along the U.S. Atlantic Coast, to determine fine-scale habitat use during the nonbreeding period. We found that M. bassanus preferentially foraged close to shore during daylight hours and used offshore areas including planned wind energy lease areas primarily for nocturnal roosting. Commuting flights between these areas peaked around dawn and could be a time of elevated risk as individuals fly to and from foraging areas. Individuals spent more time in commuting flight early in the winter and more time foraging and resting in late winter/early spring. Finally, we identified a northward migration corridor that passed through several wind energy lease areas in early spring, with migratory flights peaking in late morning. Overall, while our results suggest that offshore wind energy development in the study area will cause limited displacement from foraging habitats for M. bassanus, we highlight several locations and periods of elevated risk that could be targeted for monitoring and mitigation.