Winter bird communities in urban habitats:: a comparative study between central and northern Europe

Aim Urbanization can lead to uniformity in urban bird communities, and the general biogeographical patterns found in natural communities may not be found in urban ones. Thus, it is important to know if urbanization might be seen as contributing to a general pattern that modifies the biogeographical processes of wildlife communities. Location We studied differences in suburban bird assemblages in France and Finland. Birds in each town included in the study were surveyed using 30 ha suburban study plots located within single-family housing area and apartment block area. Methods The wintering birds were surveyed using a single-visit study plot method in January and February 1999. The level of urbanization was measured according to the general structure of the habitat by using the town maps and field notes. In addition, we counted active winter feeding stations during bird surveys. Results The average number of species was higher in France than in Finland, both in single-family house areas and in apartment block areas. The most abundant bird species occurred in most of the study sites. The urbanization level affected bird community composition more in northern Finland than in France. In Finland, the number of wintering species and their total biomass were higher in single-house areas than in more urbanized areas. The total density and biomass of birds were higher in France than in Finland in areas of apartment blocks, but not in the areas of single-houses. Urbanization level affected the total bird density only in France, being higher in areas of apartment blocks. In Finland, the total biomass of birds was higher in the single-family house areas than in the areas of apartment blocks. Most of the bird species were more abundant in France than in Finland. The habitat factors associated with the bird community variables in France and in Finland differed from one another. Feeding tables increased the species richness and the abundance of birds in Finland. Conclusions The species decrease between France and Finland was mainly because of the large proportion of species in France that are migratory in northern Finland. The abundance of urban birds did not necessarily decrease northwards. Intensive winter feeding in northern latitudes may help birds to overcome natural range limitations. Our results differed from results obtained when studying town centres and they highlight the complexity of the urbanization process across a geographical gradient.