Urban influence on birds at a regional scale: A case study with the avifauna of northern Madrid province

Bird fauna of the Madrid province (Central Spain) was analyzed according to urban development in a landscape mosaic of 700 km2. Bird distribution and abundance was studied in urban versus several rural habitats and along a gradient of urban typologies. By means of tree regression analyses we identified the most important habitat structure variables affecting bird species richness and density in urban environments. Bird communities in urban environments were globally less diverse and had higher densities than any natural habitat of the study region. The number of urban-avoider species (n = 37) was greater than the number of species favoured by urban habitats (n = 8). Current housing developments of extense crowded terraced-houses, with shortage of gardens, supported the least diverse and dense bird populations. Nevertheless, differences in bird species abundance between urban and natural habitats mitigated in many species when considering the older gardened developments. The plots with the highest species richness (average of 14.5 spp./0.8 ha) were those with 15–28% of building cover, more than 43 medium-sized trees/ha (10–30 cm dbh), and 13–54 small trees/ha (less than 10 cm dbh). Subsequently, future land-use planning should stress the exclusion of urban developments from the most valuable habitats, such as open wooded valley areas devoted to cattle-grazing (mainly ash-groves), and the negative effect of dense, low-gardened housing developments.