Miguel Ángel San Martín-Cruz

Urbanization involves changes in landscape terrain, hydrology, and vegetation. These changes allow some wildlife species to thrive in cities while blocking others. We analyzed how a gradient of urbanization in the city of Xalapa could have a filtering effect that prevents some raptors from occurring or effectively use the most urbanized areas, and where such filtering effects occur. We selected 6 habitat variables that could predict the detection and occupation of raptors along the urban gradient. We conducted direct observations and call-broadcast surveys to estimate relative abundance, richness, and diversity of raptors from June 2019–February 2020. We visited 20 sites during three seasons, from dawn–11:00 and 18:00–23:00 h. We obtained 201 individual records of 14 species. The best-preserved part of the gradient (< 7.7% urban cover) had the highest species diversity, while the 4th category along the gradient (53.9% urban cover) had the lowest, suggesting that at this level of urbanization an abrupt filtering effect occurs on the raptor community. The proportion of exotic/native plant species was the best detection predictor for most of the diurnal species and Ciccaba virgata. The proportion of urban relative to green area was negatively associated with the occupation of Accipiter cooperii and Rupornis magnirostris. Our results suggests that this Neotropical city effectively acts as a filter for most species, with only 4 raptors able to use or occupy most of the urban gradient. Our work represents a critical first step towards understanding how the process of urbanization influences a raptor community.