Influence of canopy cover and forest density on bird communities under contrasting forest management practices

Forestry practices are associated with changes in forest structure, including canopy cover and forest density, which are linked to variation in bird communities. To examine these relationships, we surveyed birds at 34 sites across three regions in South Korea between August 2022 and April 2024. Sites were classified into four categories: logged sites surveyed one (L1) or ten (L10) years after logging, and thinned sites surveyed one (T1) or ten (T10) years after thinning. Bird species were classified into foraging, nesting, habitat, and generalist-specialist guilds, and community responses were analyzed using linear mixed models, generalized linear mixed models, and N-mixture models. Overall species richness did not differ among site types; however, guild-specific responses were evident. In thinned forests, no significant differences in guild abundance were detected, whereas in logged forests, ground-feeding and edge-associated species were more abundant. Species diversity was significantly associated with forest density and canopy cover, particularly with intermediate levels of ground cover and vegetation strata above 20 m. N-mixture models further revealed species-specific associations with forest density and canopy cover. Thinned sites showed greater vertical structural heterogeneity, whereas logged sites exhibited simpler structures dominated by near-ground vegetation. Based on these associations, maintaining intermediate levels of ground cover and upper-canopy vegetation (34-66%) may help sustain bird diversity in managed forests. Spatially heterogeneous management approaches, such as temporal or patch-scale thinning, may be more effective than uniform treatments. These findings offer guidance for forest management in South Korea and other temperate plantation forests facing similar structural trade-offs.