Urban core areas are important for species conservation: A European-level analysis of breeding bird species

Natural habitats and species richness have decreased due to the urbanization. The main aim of this study was to determine whether heavily urbanized town centers can also harbor threatened bird species. Twenty-six threatened species nested in the most urbanized areas of European towns. Species-rich areas had a high number of threatened species, indicating that overall species richness could be used as a surrogate for the large number of threatened bird species. Threatened species were more likely to be found in town centers as their distribution range increased. Neither landscape nor plot-level variables explained the species richness of threatened species, which was likely due to the homogeneous habitat structure of urban core zone areas in Europe. The occurrence of Falco tinnunculus increased with increases in human density within a built-up area. The occurrence of Hirundo rustica and Muscicapa striata decreased with increases in the proportion of built-up areas in the surrounding landscape. The occurrence of Delichon urbica and Muscicapa striata decreased with increases in habitat diversity and the proportion of buildings in the study plot. The most common threatened bird species nested in cavities or buildings. The availability of suitable nesting sites or protection from predators can support the occurrence of cavity nesters in towns. We suggest that modern architecture should account for the breeding habitat needs of cavity-nesting species in building design and that urban green management must consider the occurrence of old trees with cavities or alternatively use nest boxes to support the occurrence of threatened, cavity-nesting bird species.