Identification of foraging areas and movements of Royal Tern Thalasseus maximus at the Isles Dernieres Barrier Islands Refuge, Louisiana

The Isles Dernieres Barrier Island Refuge (IDBIR) in Louisiana constitutes a major colonial seabird breeding site but is also considered a high-risk marine area that is susceptible to both natural and anthropogenic disturbances that can be detrimental to breeding areas and food resources. The objective of this study was to track the movements of breeding Royal Terns Thalasseus maximus at the IDBIR to identify important foraging movement parameters and foraging areas. GPS loggers were attached to six Royal Terns during the 2014-2017 breeding seasons. Mean foraging trip distance was 28.8 km and the maximum distance traveled was 47.8 km. The overall mean foraging area (95% fixed kernel densities) was 1042.5 ± 526.1 km2. There was individual variation among foraging area size and foraging habitats that included bays, offshore habitats, and marsh habitats. However, appreciable overlap in foraging areas included marsh habitats ~12 km north of the breeding colony and offshore areas south of the colony. Identifying seabird foraging areas is critical for understanding their resource needs in the Gulf of Mexico, the coast of which is undergoing rapid change, and to assess how major disasters, such as oil spills and hurricanes, may influence important foraging areas.