Assessing scale-dependent effects of urbanization on avian diversity.
Aggregation; N; SAD; urbanization.
Urbanization is a major driver of natural habitat reduction and fragmentation, and it has been shown that these impacts can influence species richness. However, how different components of diversity are influenced by urban intensity, patch size, and isolation between patches has not yet been mechanistically investigated. In this context, urbanization gradients are ideal for assessing how species respond to these impacts, and also allow us to better understand how local and regional changes in habitat quality influence diversity components such as: species abundance distribution (SAD), total community abundance (N), and intraspecific spatial aggregation (Agg). Here, we evaluate how two different categories of urbanization intensity (urban squares and protected areas), patch size, and its connectivity influence bird diversity patterns at various scales. To assess scale-dependent processes, 24 plots were allocated, each subdivided into 4 subplots, totaling 96 points, which were visited five times during the dry season. In these same plots/subplots local and regional environmental features were assessed. A significant reduction in species richness and abundance was observed with increasing urbanization, and this reduction was evident across all scales analyzed. However, the effect of urbanization was even stronger at plot than subplot scales, indicating a scale-dependent effect of urbanization. Furthermore, both local and regional variables, including vegetation cover and structural connectivity, were important determinants of bird diversity patterns. Thus, it is necessary to conduct practices that can reduce the intensive impact of urbanization. An example to be highlighted are actions that include more forested squares, as well as planting trees around these squares and forming ecological corridors, aiming to connect parks and green areas with urban squares.