Bird communities are affected by amount and dispersion of vegetation retained in mixedwood boreal forest harvest areas

We evaluated bird community response to type, amount, and dispersion of tre es, snags, and shrubs that were retained at harvest in mixedwood boreal for ests of Alberta, Canada. We also evaluated whether the degree of similarity between bird communities in harvest and old-growth areas was related to th e type and amount of materials retained at harvest. We combined data from t hree separate studies to generate a large data set covering a wide range of cut-block structures. Birds were surveyed using point counts and line tran sects. Residual vegetation was surveyed partially on the ground, and partia lly from aerial photographs. Bird species commonly associated with parkland and open country habitats had high densities in harvest areas that contain ed abundant shrubs and few residual trees or snags. Within harvest areas wh ere more trees, particularly large deciduous trees, were retained, and when those trees were retained in clumps, bird communities were more similar to those found in old-growth forests. Thus, by retaining clumps of large tree s and snags in harvest areas managers may be able to create habitats that a re used by old-growth forest bird species. However, for many forest birds, density was lower in cut-blocks with residual trees and snags than it was i n old-growth forest. Results should be interpreted cautiously because survi val and reproductive success of forest birds in cut-blocks with residual tr ees and snags was not determined. (C) 2000 Elsevier Science B.V. All rights reserved.