Avian habitat relationships at multiple scales in a New England Forest

Habitat selection by birds is a complex phenomenon that varies by species and community. Some birds select habitat according to specific combinations of microhabitat character- istics, which pertain to the structure and composition of site-specific vegetation. Recently, however, habitat selection studies have shifted from site-specific characteristics to consideration of coarser environmental scales. We examined habitat relationships for 31 bird species in the White Mountain National Forest at a series of scales from microhabitat (fine scale) to the landscape (coarse scale). Relative abundance data were collected through 10 min. point counts at 360 points organized into 15 transects. Habitats sampled included a diversity of forest-cover types (deciduous to coniferous) and management strategies (wilderness to clearcuts). Species-specific logistic regression models based on subsets (183 and 48 points) of the original dataset corroborated the historical focus on microhabitat, but models including other scales indicated that some birds respond to coarser scale environmental characteristics. These results also supported the premise that some birds respond to multiple environmental scales. Community gradient descriptions, based on canonical correspondence analysis (CCA), supported results of logistic regression, indicating that microhabitat constituted the most important level followed by lesser, but significant, contributions from other scales. Through species-environment biplots, CCA also effectively illustrated avian habitat selection as a multiple-scale phenomenon, showing the hierarchical organization of landscape components and how they affect the spatial distribution of bird communities. FOR. SCI. 48(2):243-253.