The influence of wildfire, logging and residual tree density on bird communities in the northern Rocky Mountains

Abstract

By emulating natural disturbances like wildfire, managers hope to maintain biodiversity in managed forests. Leaving residual live trees in harvested areas is an important component of this strategy. However, the influence of this approach on songbird communities is largely unknown. We surveyed songbirds in 166 stands in the Rocky Mountains in BC, Canada, that had been logged or burned by wildfire. Stands were located in mid or high elevation biogeoclimatic zones, and varied from 7 to 45 years since disturbance and in density of residual trees from 0 to 320 conifer overstory, 0 to 832 conifer understory, and 0 to 68 broadleaf trees/ha. Although differences in bird communities between burned and logged stands of similar ages were detected, these differences were not consistent between biogeoclimatic zones, nor did they explain a large amount of the variation in bird communities. Logged stands had a higher density of birds, but expected species richness did not differ between logged and burned stands. All but a few rare species were detected in both disturbance types. Of 26 species analysed in detail, densities of 14 were greater in logged stands, 6 were greater in burned stands, and 6 were not significantly different between disturbance types. The bird community, bird abundance and densities of individual species were influenced by residual tree density and type. As time since disturbance increased, bird communities in burned and logged stands in the Engelmann Spruce-Subalpine Fir zone became more similar, but those in the Montane Spruce zone became less so, likely due to differences in residual tree density. Results suggest differences in bird communities in logged and burned stands ≥7 years post-disturbance are mainly in abundance rather than community composition, but abundances of individual species can be significantly influenced by residual tree density and type. Managers can influence the abundance of some species in harvested areas by manipulating the type and density of residual trees. © 2006 Elsevier B.V. All rights reserved.