Bird responses to partial retention timber harvesting in central interior British Columbia

Current legislation in British Columbia, Canada, requires patches of forest to be left uncut within timber harvest blocks during commercial logging operations, to maintain wildlife diversity in the post-harvest stand. To rest the effectiveness of this practice. we compared bird content in (i) conventional clearcuts (all trees removed), (ii) clearcuts with partial forest retention (15-22% of the stand), and (iii) mature uncut stands in sub-boreal conifer forest in central interior British Columbia. The forest and the partial retention sites had similar numbers of species and similar numbers of birds in total (per transect km) in all three years. The clearcuts had fewest. The partial retention sites contained species from the forest, species from the clearcuts, acid species found at neither of the other two site types. Some forest-dwelling species were missing from the partial retention sites, and some were less abundant, but others were more abundant at the partial retention sites. Within sites, species distributed themselves among habitat structure-types by nesting/foraging 'guild'. Tree-containing habitat types (uncut forest patches, riparian strips) were preferred by most species (occupancy versus extent), but some preferred open ground or remnants of the former understorey. Subject to the question of sustainable breeding, these findings suggest that partial retention harvesting (i) succeeded in maintaining most of the forest bird community, and (ii) increased the total bird diversity. These results were obtained at higher cut:leave ratios than have been reported hitherto. (C) 2001 Elsevier Science B.V. All rights reserved.