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The expansion of cities is one of the main causes of the global decline of biodiversity, but bird communities can respond surprisingly differently to this threat at different times of the year. This is what emerges from the research “Different traits shape winners and losers in urban bird assemblages across seasons“, published today in the prestigious journal Scientific Reports and the result of a collaboration between researchers from several Italian and foreign universities, under the guidance of the National Biodiversity Future Center (NBFC). Coordinated by Riccardo Alba, researcher at the Department of Life Sciences and Systems Biology of the University of Turin and the Bird Lab Turin, the study analyzed how bird species respond to urbanization along a gradient that goes from city centers to rural outskirts. The research, which involved the Italian cities of Turin, Milan, Florence, Rome, Naples and Campobasso, adopted a multi-seasonal approach, including both the reproductive and winter periods, to fully capture the complexity of urban ecological dynamics. Particular attention was paid to the functional traits of the species – such as diet, reproductive strategy, social behavior and nesting methods – to understand which characteristics favor or penalize the different species in urbanized environments.
Solitary and opportunistic species
The results show that some species, defined as “winners”, are able to thrive in cities thanks to colonial nesting, a high number of clutches or a long lifespan. In winter, however, solitary and opportunistic species prevail, with a generalist diet. In contrast, “loser” species tend to be insectivorous, migratory and nest on the ground – characteristics that make them vulnerable to habitat loss and pressures of the urban environment. However, most species fall into the category of “urban adapters”: not completely favored by urban environments, but still able to effectively exploit contexts with an intermediate level of urbanization. Furthermore, some species show remarkable seasonal adaptation capabilities, frequenting urban areas in winter but not during the breeding season and vice versa.
Urban parks
Turin stands out among the large cities of Northern Italy for its exceptional extension of green areas and urban parks, which create an urban mosaic capable of hosting a remarkable diversity of birds, including those typical of forest environments. Large urban parks such as Parco della Colletta, Meisino, Valentino and Pellerina offer suitable habitats for many sensitive species, often rare in other metropolitan contexts. In some of these parks, for example, species such as the marsh tit, the common treecreeper and the nuthatch can be observed, but rarer species also nest, such as the lesser spotted woodpecker, the black woodpecker, the stock dove or the hobby.
A real ecological corridor
A key role is also played by the Turin hill, which with the Superga Hill Natural Park represents an important green lung close to the city, acting as a reservoir of biodiversity and a nesting area for many species. Furthermore, the Po river, with its tree-lined peri-fluvial strips, acts as a real ecological corridor, facilitating movement and the connection between the urban green areas and the surrounding natural areas. These elements, including the large tree-lined avenues of the city, make Turin a virtuous example of how cities can concretely contribute to the conservation of biodiversity, even of more demanding forest species. At the same time, the presence of a rich and diversified fauna in urban green areas improves the quality of life of citizens, offering opportunities for contact with nature. Thus urban biodiversity becomes a social and cultural heritage to be enhanced.
Seasonal variations
"The study - says Riccardo Alba - highlights the extraordinary ability of birds to adapt to a wide range of environmental conditions, even within landscapes heavily modified by man. Taking seasonal variations into account is essential to fully understand the ecological responses of species to urbanization. This approach can help improve the planning of urban fabric, making it more sensitive to the needs of wildlife and more effective in promoting sustainable and biodiversity-rich cities". (Source: University of Turin Press Office).
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