Seasonal patterns of habitat use of resident birds in Białowieża Forest and its links to post-disturbance management

Resident bird species staying in the same area year-round may face very different habitat conditions between seasons in temperate forests. This may cause resident forest birds to use different habitats during winter and spring. Furthermore, habitat use and their seasonal shifts could be additionally affected by large scale forest disturbances (e.g. outbreaks of bark beetles) and post-disturbance management, as they likely affect the availability of crucial resources for reproduction and survival. We investigated the impact of the European spruce bark beetle (Ips typographus) outbreak and post-outbreak management on winter and spring habitat use of 18 resident bird species in Bialowieza Forest, Eastern Poland. We showed differences in habitat use of resident birds in winter and spring, at the level of species, community and three foraging guilds (i.e. invertivore bark foragers, invertivore arboreal gleaners and omnivores). First, bird species richness and bird abundance recorded at 111 sites in winter were not related or even showed a negative relationship with richness and abundance in spring, indicating that winter and spring bird diversity hotspots did not spatially overlap. Second, the wintering community as a whole, and the invertivore arboreal gleaners in specific, shifted their density towards more coniferous sites and increased their density at moderately salvage-logged sites, while decreasing their density at strongly salvagelogged sites. The wintering invertivore bark foragers shifted towards more outbreak sites (i.e. both salvagelogged and natural regeneration) and distributed more evenly along the natural regeneration - salvage-logged gradient. The distributions of habitat use were species-specific and there was no single habitat or level of disturbance preferred or avoided by all species or groups in spring or winter. This study highlights the importance of considering habitat use outside of the breeding season, when assessing habitat requirements of resident forest bird communities to evaluate the impact of post-disturbance management. In addition, it shows the significance of maintaining the heterogeneity of forest habitats to the wintering resident bird community, especially when deciding on post-disturbance management actions.