What determines occurrence of threatened bird species on urban wastelands?

Bird species of cultivated landscapes have been declining dramatically for decades. The main cause for this decline is intensified agricultural practice. At the same time, worldwide urbanisation increases and has severe impacts on land use. Urban wastelands, i.e., unused land within urban agglomerations, are known to provide habitat for endangered animals, but to date systematic research on birds is rare. We aim at assessing environmental characteristics of urban wastelands that meet the requirements of rare and declining bird species. In the city of Berlin, Germany, we surveyed birds on 55 wasteland sites dominated by sparse vegetation. Our analysis includes quantitative measurements of residential human density and degree of sealing at different spatial scales, a detailed vegetation mapping, and data on human intrusion. Boosted regression trees were used to model the occurrence of eight bird Species of European Conservation concern (SPEC). Overall we found 12 SPEC species; for eight data were sufficient to built models. Our findings reveal that the occurrence of endangered bird species depends most strongly on area size and vegetation structure and to a lesser extent on the composition of the urban matrix. On-site features accounted for roughly two third of the explained variance and degree of urbanisation in the surroundings for the remaining one third. Intrusion of humans or dogs had no measurable negative effect on species occurrence. As a rule of thumb, plots above 5 ha harbour SPEC species, those above 7 ha are valuable for several sensitive open-land bird species. We show that wasteland habitats have potential for nature conservation that should be considered by urban planners and landscape architects. Knowledge about crucial habitat features (few trees and shrubs, sparse vegetation) enables us to create and maintain urban green spaces that enhance protection of rare and declining species. Urban wastelands may not have the potential to fully compensate for changes and population declines outside urban areas, but they may help to offset the loss of biodiversity in the countryside. (C) 201 2 Elsevier Ltd. All rights reserved.