Short-term responses of breeding songbirds to a gradient of broadleaf removal in managed mixedwood forests in British Columbia, Canada

Brushing is a silvicultural practice that reduces regenerating broadleaf vegetation in young conifer plantations. Despite its widespread use, the effect of brushing on breeding songbirds is poorly understood, especially across a gradient of broadleaf retention. We evaluated how upland forest-associated songbirds respond to four broadleaf retention treatments—control (no broadleaf removal), high retention, low retention, and full removal—using 6 randomized treatment blocks near Prince George, British Columbia, Canada. We collected automated acoustic point counts for one year pre-treatment (2023) and two years post-treatment (2024 and 2025) in stands ranging from 7–10 years post-planting. We used a Before-After Control-Impact design to assess change in community diversity (alpha, gamma, and beta diversity) and species-level relative abundance using two point count methodologies (truncated and unlimited-distance point counts). Relative to the control, alpha species richness and Shannon diversity showed small declines in all treatments with confidence intervals overlapping zero. Gamma species richness declined most strongly under low retention and moderately under full removal, while high retention showed little change. Beta diversity was similar between before and after periods for all treatments and was dominated by species replacement rather than species loss. Species-level analyses revealed greater variation in responses but most treatment effects were weak and characterized by wide confidence intervals. Inferences were broadly consistent between point count methodologies. Overall, our results suggest that short-term responses of breeding songbirds to brushing are limited and context-dependent. Further monitoring is needed to determine if treatment effects exhibit a temporal lag and whether brushing alters longer-term trajectories of breeding bird communities.