Avifauna homogenisation by urbanisation:: Analysis at different European latitudes

We studied the homogenisation effects of urbanisation on avifauna in towns of three countries selected along a latitudinal gradient: Italy, France and Finland. In each town (n = 19), numbers of species were analysed along an urbanisation gradient using two urban sectors (centre and suburban) and one non-urban sector (periurban), representing the regional species pool. Firstly, we compared the avifauna by using species richness and similarity indexes along the urban gradient (S) and latitudinal gradient (L). In Europe, the number of exotic bird species in towns was low. The number of species decreased from the periurban and suburban sectors to the centre sector. Thus, the generally low number of species and few dominant birds indicate that urban bird communities are structurally simple. In addition, many habitat specialists were lacking from urban centres. The centre species represented about 43% of periurban species (similarity S). There was no correlation between town size and species trend in sectors. However, bird community similarity L was lower between town centres than between periurban areas. Latitude explained 89% of the species difference in periurban sector but only 52% in the centre, supporting the homogenisation effect of urbanisation. Secondly, we examined the homogenisation effect through the variability of some specific life-history traits (diets, nest heights, feeding habitats) by using data on Passeriformes. Our results suggested that urbanisation might cause homogenisation by decreasing the abundance of ground nesting bird species and bird species preferring bush-shrub habitats. Urbanisation appeared a cause of taxonomic homogenisation of the avifauna but the effects of latitude and urban habitat diversity may make generalisation difficult. (c) 2005 Elsevier Ltd. All rights reserved.