Seasonal variation in patch and landscape effects on forest bird communities in a lowland fragmented landscape

Abstract In fragmented temperate landscapes, species responses to patch and landscape structures are likely to vary across seasons. However, few studies have examined the dynamic effects on biodiversity across seasons. We examined the effects of patch attributes and connectivity and seasonal variation in the effects of these environmental variables on forest bird communities at woodland fragments surrounded by agricultural land across three seasons (breeding, dispersal, and wintering seasons). We surveyed birds in woodland remnants and examined the effects of patch area, woodland connectivity, woodland type, and three interaction terms between these environmental variables and season (patch area × season, connectivity × season, and woodland type × season) on forest bird communities. In the results, species richness, abundance and composition of forest bird communities were associated with patch attributes and connectivity, and some of these associations varied depending on the season. Specifically, there were significantly higher abundances of specialist birds in riparian woodlands compared to conifer woodlands during the breeding season, whereas this pattern was reversed during the winter. In addition, we found the negative effects of patch area during the dispersal and wintering seasons and the positive effect of connectivity during the dispersal season on generalist bird abundances. These results suggest that woodland patches with high conservation values differ among three seasons. The conservation planning for a fragmented landscape therefore needs to consider the role of patch attributes and connectivity during multiple seasons rather than just the breeding season.