| Summary: | Thesis (M.S.)--Humboldt State University, Natural Resources: Wildlife, 2010 Global climate cycles can affect demographic rates and drive local and regional dynamics of bird populations. Local-scale studies of individual species have identified associations between the El Ni??o-Southern Oscillation (ENSO) and survival rates and productivity of birds. Broad-scale studies of demography and climate are needed to better understand the effects of climate throughout the life cycle. I examined the impact of broad-scale climate indices on apparent survival of Russet-backed Swainson's Thrush (Catharus ustulatus ustulatus) captured on their breeding grounds in western North America (N = 10,870). I developed 69 a priori models that included effects of ENSO, the North Atlantic Oscillation, the Pacific Decadal Oscillation, latitude, region, and residency status on survival and compared their QAICc scores using program MARK. The most parsimonious model included an ENSO effect, a regional effect, and a residency effect on survival and was 44 times more supported than the nested model that did not incorporate ENSO. ENSO had a significantly positive effect on survival probability, was significantly correlated with precipitation anomalies in the migratory and winter range, and was positively associated with variation in wing chord. These results suggest that survival of this Neotropical migrant is influenced by ENSO-related precipitation variability in its winter range, migratory pathway, or both. If, as some climate models predict, annual variation in ENSO increases, Russet-backed Swainson's Thrushes may suffer greater variation in annual survival. Directly associating climate with key demographic parameters provides a powerful approach to predicting a species' response to climate-change.
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