Effects of prescribed burns on wintering cavity-nesting birds

Primary cavity-nesting birds play a critical role in forest ecosystems by excavating cavities later used by other birds and mammals as nesting or roosting sites. Several species of cavity-nesting birds are non-migratory residents and consequently subject to winter conditions. We conducted winter bird counts from 1998 to 2000 to examine the abundance and habitat association of cavity-nesting birds in prescribed burned and unburned ponderosa pine (Pinus ponderosa) stands. Even though bird diversity indices did not differ between burned and unburned stands, species-specific bird abundance was associated with habitat variables in three burned and four unburned stands. Total cavity-nesting bird abundance was greater in burned stands. Most cavity-nesting birds were observed in mixed-species flocks. Individual species of these flocks were associated with different habitat variables within stands. Numbers of woodpeckers were significantly greater in burned stands and numbers of chickadees were significantly greater in unburned stands. Bark foragers such as woodpeckers (Picoides spp.) and pygmy nuthatches (Sitta pygmaea) were associated with fewer small trees and recently decayed snags and logs. Foliage gleaners such as the chickadees (Poecile spp.) were associated with small diameter snags. The juxtaposition of burned and unburned stands is important for individual birds reliant upon other members of a mixed-species flock and habitat heterogeneity within stands is important for maintaining a diverse cavity-nesting bird assemblage.