Disentangling the influences of habitat availability,heterogeneity and spatial position on the species richness and rarity of urban bird communities in a central European city

The prominent role of the absolute amount of (semi)natural habitats on urban avifauna richness is well documented; however the relative role of habitat availability, heterogeneity and spatial position at the scale of a whole city has not been investigated so far. The main objective of this study was to evaluate the relative influence of these variables on the species richness and rarity value of bird communities in the city of Prague, Czech Republic. We used three modes to describe the urban environment, resulting in different habitat category resolutions. Coarse habitat descriptors were good enough for predicting species richness, but a more detailed resolution was better in explaining the distribution of communities comprising rarer species. The availability of wooded habitats was consistently the most important variable explaining both richness and rarity of bird communities. Habitat heterogeneity enhanced species richness, especially in highly urbanized areas where wooded habitats were scarce. However, rarer species responded to habitat heterogeneity only weakly. The influence of grid cell spatial position on bird community richness was overridden by the impacts of habitat availability and heterogeneity. However, communities comprising rarer species tended to breed at peripheral sites encompassing open habitats and large woodlands. The preservation of sufficient wooded habitats including small patches remains the key tool for bird conservation in cities, and habitat heterogeneity should be supported in areas with less than ca. 3 % of wooded habitats. Rarer species benefit from the maintenance of more extensive patches of greenery in peripheral urban areas.