Bird-habitat relationships in grand fir forests of the Blue Mountains, Oregon.

摘要

During the breeding seasons of 1994-1996, we sampled bird communities and habitat characteristics in grand fir (Abies grandis) forests of the Blue Mountains, northeastern Oregon (USA), at the stand- and landscape-level with the objective of explaining variation in the composition and abundance of forest avifauna. We analysed data from 77 forest stands that varied in size from 16 to 213 hectares. Canonical correlation analysis (CANCOR) indicated that stand-level features accounted for more variance in the relative abundance of bird species than did landscape-level features (35 versus 14%, respectively). The most important stand-level features were overstorey canopy cover, density of large-diameter live trees, and understorey structure (especially herbs and shrubs). Important landscape features for predicting the abundance of species within a forest stand included stand isolation and the percentage of surrounding landscape within a 4-km radius that was occupied by forest cover. Using the information-theoretic approach to model selection and inference, we built models of bird-habitat relationships to forecast abundance of 24 species. Consistent with CANCOR results, species-specific habitat models were dominated by stand-level variables. Overstorey cover was a significant predictor of abundance for 17 of 24 species modelled (71%). We conclude that in forests represented by our sample, management for most avian species can be usefully focused on within-stand dynamics of structure, but that efforts to forecast abundance of some species can be enhanced by integration of landscape metrics as well..