Seasonal dynamics and ecological correlates of population abundance of birds inhabiting green areas within a megacity

The expansion of cities has had severe effects on biodiversity. However, within cities, green areas are suitable habitats for diverse species, both native and exotic. This study quantified the population abundances and temporal variations of 16 native and four exotic species of birds that inhabit urban green areas of Mexico City, which is considered a megacity. We used N-mixture models to estimate the abundance of these species. These demographic models also estimate their detection probabilities. We found that six species of birds (three native and three exotic) had remarkably higher abundances than the rest of the species. Eight species had seasonal changes in their abundances, with six of these species increasing in numbers during the dry season and the other two species being more abundant during the rainy season. Some native bird species had higher population numbers in parks with large trees of diverse species, abundant flowers, less urban cover, and low noise levels. In contrast, exotic species were more abundant in parks with intense human activity, where they can easily find anthropogenic food sources. Our findings provide fundamental information about the ecological traits of urban green areas that allow native and exotic birds to thrive in urban ecosystems.