Nest-site selection and nest survival of two woodpecker species in ponderosa-pine dominated forests
Story, Scott Joseph.
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Management of woodpecker populations requires knowledge of nesting habitat and vital rates in different forest conditions. We examined nest-site selection and nest survival for two woodpeckers, northern flicker (Colaptes auratus) and hairy woodpecker (Picoides villosus) at three locations in ponderosa-pine forests of the interior Columbia River Basin. Our goals were to: (1) characterize the range of habitat conditions available to nesting woodpeckers in our study area; (2) determine which habitat features best discriminated between nest and non-nest plots, and (3) establish which habitat features most influenced daily nest survival. Northern flickers and hairy woodpeckers were more likely to choose snags than live trees. Both species used larger diameter snags than those available at random. Nest snags tended to be in plots that had higher snag densities and lower live tree densities. For northern flickers, a model of constant daily survival received more support than any model containing habitat covariates.Daily nest survival from the best model for northern flickers was estimated to be 0.55 (95% CI: 0.46-0.64). Increasing live tree density and coarse woody debris volume were included in the most well supported model for hairy woodpeckers. Results from this study did not provide support for the "nest-quality" hypothesis. Nest survival for woodpeckers in this study was low, especially at the Idaho location; we hypothesize that this could be because of differences in predator abundance among the three locations. In ponderosa pine forests that have not been recently disturbed, we recommend maintaining clumps of snags, especially those that contain large snags. Further research is needed to understand the mechanisms that dictate woodpecker nest survival in ponderosa pine forests.