| Considerations of spatial and temporal scales are important for understanding the distribution of highly mobile migratory birds, because habitat selection can involve hierarchical processes from the landscape to nest site scale. The aim of this thesis was to evaluate the importance of predation, intraspecific competition, biophysical habitat features and prey abundance in determining the distribution of breeding Harlequin Ducks Histrionicus histrionicus in northern Labrador. This was assessed at several spatial scales, both within and among years. Results indicate source-sink metapopulation structure at the landscape scale, with glacially carved river canyons containing sub-populations. Availability of cliff nesting habitat and, subsequently, abundance of birds of prey is a likely mechanism determining demographic differences among sub-populations of Harlequin Ducks along the source-sink gradient. Results provide empirical support for aspects of several theoretical areas, including application of a metapopulation framework to migratory birds, coexistence of predators and prey through spatial dynamics, spatial and landscape influences on population dynamics and demographics, and the importance of considering multiple spatial and temporal scales in ecological research. (Abstract shortened by UMI.). |
