Mimicking the mountains: Using spatial characteristics of unharvested habitat to guide working forest management for a rare, forest-dependent songbird

Management of the rare Bicknell’s Thrush (Catharus bicknelli) is increasingly a forestry-driven challenge, as most nesting habitat in Canada now occurs within working forest landscapes. This species primarily nests in short, dense red spruce (Picea rubens) and balsam fir (Abies balsamea) forests generated by natural disturbance and regenerating timber harvests in northeastern North America. While structural requirements of the species’ habitat are known, information about the amount and arrangement of these patches would aid foresters with timber harvest planning. Using remotely-sensed data and citizen science point count surveys, we define the specific configuration, structure, and composition of forest patches. Our results suggest that aggregated patches of short, dense, spruce-fir forest are preferred over non-aggregated patches of the same total area. Sites where Bicknell's Thrush were detected contained nearly double the amount of dense spruce-fir habitat (mean = 20.15 ha) compared to unoccupied sites (mean = 11.89 ha). Evaluation against datasets from harvested forest landscapes confirmed the spatial relationships identified in unharvested mountain habitats and reliably predicted thrush abundance. We recommend using even-aged silviculture to maintain a shifting mosaic of >20 hectare spruce-fir stands to maintain nesting habitat analogous to the natural landscape mosaics to which the species is evolutionarily adapted.