WHAT DO MIGRANTS DO DIFFERENTLY? IDENTIFYING HABITAT FOR PARTIALLY MIGRATORY POPULATIONS.
Derek B. Spitz; University of Oregon; P.O. Box 1676, Bishop, CA, 93515; (831) 737-3120; spitzderek@gmail.com; Mark Hebblewhite, Thomas R. Stephenson
Migratory species are threatened by global declines, but our ability to conserve these populations is often limited by our understanding of the relationship between migratory behavior and habitat. Most migratory populations are partially migratory, displaying both migration and year-around residency. The resource hierarchy hypothesis predicts that the most important resource limiting a species distribution act at the coarsest spatial scales. Building on this foundation, we hypothesized that migration and residency represent contrasting scale-specific approaches to managing trade-offs between forage and predation risk, and that the distribution of migrant and resident habitats can predict the local prevalence of migration. To test these hypotheses, we quantified migratory status- (resident/migrant) specific differences in winter resources selection by federally-endangered Sierra bighorn (Ovis canadensis sierrae) across three spatial scales. Residents showed stronger coarse-scale selection for safety from predators and stronger fine-scale selection for forage, while in migrants this pattern was reversed. Spatial predictions from our coarse-scale resource selection models strongly predicted the local prevalence of migration (pseudo R2 = 0.87). This analytical approach provides a novel basis for estimating the prevalence of migration across large landscapes. Our results can inform a variety of management actions including reintroductions and translocations.
Ecology and Conservation of Mammals I