Can forest management have season-dependent effects on bird diversity?

Abstract

Forest management modified the original structure of most European forests, and in the most extreme cases, genuinely natural and semi-natural forests were turned into plantations through clear felling and replanting, often using non-native species. We compared the bird community structure of native oak woods of northern Italy with that of their anthropogenic counter-parts: black locust and sweet chestnut woods. The three stand types were compared in terms of vegetation structure, bird species richness, diversity and abundance of foraging guilds. We analysed both the overwintering and the breeding community, to assess whether management had specific seasonal effects on bird diversity. Forestry-imposed disturbances affected bird diversity more consistently in winter than in breeding time: bird species richness and diversity were significantly greater in oak and chestnut stands, which were the preferred habitat for bark foragers and foliage gleaners. In the breeding period, bird diversity of black locust woodlands increased, and inter-stand differences were not significant. At this time of year, understorey gleaners were more abundant in black locust stands (where shrubs were denser). In winter, species richness, diversity and the abundance of several guilds were positively correlated with stand age, whereas in the breeding period canopy gleaners preferred younger woodlots. Despite the lack of inter-stand differences in breeding bird diversity, young-managed woods benefited generalist birds that need no particular conservation efforts. Conversely, priority species for forest conservation such as specialised bark foragers positively selected native and mature stands throughout the year. We suggest that detailed year-round studies on diversity and community composition could sharpen the precision with which it is possible to prescribe conservation measures in forested areas.