Urbanization and stability of a bird community in winter

The main objective of this study was to analyze between-winter stability of bird communities along latitudinal (950 km) and urban gradients (from small village to towns) in Finland. Birds were surveyed at the same 30-ha study plots using the same methods in 31 villages and town centres in the winters of 1991-1992 and 1999-2000. Species richness did not differ between the 2 study winters, but variation in total abundance of birds increased with increasing urbanization. However, urbanization reduced variation in wintering bird community structure. Species richness, density of wintering birds, and dissimilarity of wintering bird communities did not vary with latitude. According to our results, the level of urbanization was a more important factor than latitude in explaining the structure of the bird community in winter. We assume that the presence of a continuous, rich, and diverse supply of food offered by humans with increasing urbanization may explain variation in species abundances and stability in urbanized ecosystems.