Urbanisation impacts avian biodiversity on stream ecosystems – insights from a large geographical scale

Urban blue and green spaces, such as streams and adjacent riparian areas, constitute important biodiversity refuges in highly anthropogenically -modified areas, but this depends on their ecological characteristics, preservation and management. Birds are useful indicators of ecosystem quality due to their relatively high trophic position. They may also disseminate and control pathogenic organisms, being good indicators for human and animal health risks. In our study, we used presence/absence data of avian species, and a wide environmental characterization of 102 urban streams across five European cities with a broad latitudinal range (Portugal, France, Italy, Belgium, and Norway), to evaluate how the impacts of urbanisation on ecosystem health impacted avian biodiversity. Benevento and Oslo differed most strongly from the remaining cities. The most representative bird species were different among the cities, which indicated that there is not a full homogenization of in European riparian zones. Yet, the number of insectivorous bird species was negatively associated with increasing urbanisation, including some of its proxies such as imperviousness, artificial light at night and population density. Streams with higher diversity of vegetation types and habitats tended to favour insectivorous birds like the Eurasian Wren Troglodytes troglodytes and the Common Chiffchaff Phylloscopus collybita. This is relevant in the context of One Health because this feeding guild may control the abundance of potential disease vector-mosquitoes. Management strategies should focus on preserving and rehabilitating riparian zones with structured vegetation and promoting habitat diversity through the maintenance of hedgerows and patches of natural green areas.