Urbanization promotes bird colour homogenization
Leveau, Lucas M.
Urbanization acts as an environmental filter that allows bird species with certain ecological traits, such as a generalist diet and nesting on buildings, to occur in urban centres. However, its effect on other bird traits, such as plumage colour, has still not been studied. The objective of this study was to analyse changes in plumage diversity and composition along urbanization gradients of three cities in central Argentina: Mar del Plata, Balcarce and Miramar. Bird surveys were made in urban, suburban and rural areas using transects during two breeding seasons. Colour description and bird size were obtained from the literature. Colour diversity was calculated using functional diversity indices: FD and FDis. Null models that control for species richness were used to estimate standardized effect sizes. Colour composition was analysed using Non-metric multidimensional scaling. FD and FDis decreased with percentage of impervious cover and increased with habitat diversity, whereas FDis also showed an interaction between city type and impervious cover. After both indices were controlled for species richness, they showed decreases with impervious cover and effects of city type. Highly urbanized areas were dominated by grey colour, plumage dimorphism, polymorphism and small and medium sizes. Sites with high habitat diversity were inhabited by species of yellow and green coloration, whereas rural areas were occupied by large species with combinations of black, brown and white. Not only are there fewer species in more urbanized areas, but they look more similar than expected by chance. These results suggest that urbanization acts as an environmental filter for bird colours, allowing the presence of birds with similar colours.Show more [+] Less [-]