Dynamic rates of site occupancy by native birds in an urban ecological reserve

Abstract

AbstractUrban ecological reserves are relatively large green areas immersed within cities that serve the purpose of preserving the native species of plants and animals that still persist in urban settings. In this study, we examined temporal changes (among seasons and years) in site occupancy rates of nine species of native birds that inhabit an urban ecological reserve located within one of the largest cities in the world, Mexico City. Using data collected during 11 field seasons that spanned a four-year period and implementing multi-season occupancy models, we estimated occupancy, colonization, local extinction, and detection probabilities of all nine species. For more than half of our study species, the highest occupancy and colonization rates occurred at or near the urban areas that surround the reserve. Additionally, in three species local extinction probabilities were lowest also at these urban sites. This urban affinity can be explained by the diverse vegetation that prevails in the surrounding urban sites, which offers a high habitat heterogeneity that facilitates the presence of bird species with distinct ecological needs. In contrast, the ecological reserve consists of a relatively homogeneous xerophytic scrubland where a few species of shrubs and small trees are dominant. We did not detect long-term decreasing trends in site occupancy of any species. Instead, in three species we observed positive trends in occupancy during particular periods. Overall, our findings indicate that the combination of this urban ecological reserve with the green spaces of the surrounding urban areas harbors stable populations of native birds.