Protecting birds in protected areas: a multi-scale analysis of forest structure and species occurrence

Protected areas are cornerstones of avian conservation, yet forest-associated bird communities continue to decline even within protected lands. The capacity of a protected area to sustain bird populations depends on both internal habitat quality and the surrounding landscape context, yet the relative importance of these scales remains poorly understood. We evaluate how forest structure at three nested spatial scales (local, park, and county) influences the occurrence of forest-associated birds within protected areas. We analyzed 17 years (2006–2023) of point count data for 16 forest-bird species across eight National Parks in the Northeastern United States to determine the relationships between species occurrences and five forest-structure variables, including the dominant spatial scale for each. Forest-structure variables were derived at local, park, and county spatial scales using long-term park monitoring and national forest inventory data. County-scale forest variables were selected most frequently as the dominant scale of effect on bird occurrence probabilities (19 species-covariate combinations), followed by local (16) and park (5) scales, with at least one county-scale forest variable influencing 75% of species. All but two species showed significant associations with forest structure variables. Park size had weak and inconsistent effects on occurrence, likely because the parks included in our study are all small. While these parks contain quality avian habitat, county-scale forest availability and connectivity may constrain which species persist within them. Protected areas cannot conserve forest-associated birds in isolation; regional landscape context at the county-scale is an equally important determinant of species occurrences, especially for small, protected areas. Management of the matrix habitat surrounding protected areas, such as restoring forest availability and improving connectivity, may yield greater conservation returns than management of protected areas in isolation. This can be a tractable strategy for practitioners in regions where expanding formal protection is constrained by competing land uses.