Seasonal changes in bird species diversity at the interface between forest and reed-bed

Habitat edges are landscape structures that have a major influence on animal communities. Bird communities' response to habitat edges is influenced by the season and habitat characteristics but it is still poorly understood how communities respond to structural complex (i.e. natural) edges. Inter-seasonal changes in bird species diversity were quantified at a homogeneous, sharp interface between two habitats that host distinct and well-represented bird communities: a mature broad-leaved forest and a compact reed-bed area. Resident species diversity was found higher during winter, both in terms of species richness and evenness. The presence of the reed-bed nesting migrants during the summer season did not notably modify the seasonally reversed diversity pattern; the overall evenness was higher during the winter season while the overall species richness did not differ between the two seasons. Thus, contrary to the expected regional seasonal diversity pattern, the forest – reed-bed interface is, in winter, a local bird diversity hotspot. The possible causes and implications for conservation of this phenomenon are discussed.