Seasonal variation in climate and landcover niches of a migratory bird

Abstract Background: Resource utilization strategies of avian migrants are a major concern for conservation and management. Consequently, the ability to predict potential shifts in migratory species spatial use and migratory behaviour is a pressing challenge for predictive ecology under global changes. There are two main strategies of resource use adopted by migratory birds: niche tracking for similar environmental conditions and niche switching between different environmental conditions between seasons. Our objective was to examine whether the niche tracking/niche switching hypothesis would better explain seasonal variations in the ecological niche overlap of the American White Pelicans (AWPE, Pelecanus erythrorhynchos). We also tested whether recent changes in the non-breeding ground land-use have altered habitat selection and space use by AWPE. Methods: We used Dirichlet-multinomial models to detect differences in habitat selection between regions and over times with the GPS locations of 36 tracked AWPEs. We estimated climatic and land-cover niche overlap between the breeding and non-breeding grounds to test for niche switches between seasons using ordination methods. Results: Our habitat selection models did not detect shifts in habitat selection by AWPE after 2005. American white pelican strongly selected open water and wetland at the non-breeding and breeding grounds. American white pelicans showed little climatic niche overlap but substantial landscape niche overlap between breeding and non-breeding grounds.Conclusions: Declines in aquacultural acreage did not change AWPE habitat selection in the Northern Gulf of Mexico. Our results did not support the hypothesis that AWPE would be a climatic niche tracker. However, AWPE tracked its foraging habitats, exhibiting strong selection for open water and wetland at both the breeding and non-breeding grounds. Climatic niche switching suggests that AWPE may adapt to future climate changes.