Dynamic occupancy analyses of native birds in an urban ecological reserve reveal seasonal changes in site occupancy and preference for adjacent urbanized areas

Urban ecological reserves are large green areas immersed within cities where native and exotic species of plants and animals coexist. Here, we examined the environmental features that facilitate the occurrence of nine species of native birds in an urban ecological reserve located within one of the largest cities in the world, Mexico City. We also searched for changes in occupancy rates among the three distinct climatic seasons that occur in central Mexico: warm-dry, rainy, and cold-dry. Using data collected during four years and multi-season occupancy models, we found that most of our study species prefer the urbanized sites that surround the reserve over the core conservation areas. This urban affinity can be explained by the diverse vegetation that prevails in such urban sites, which offers a high habitat heterogeneity that facilitates the presence of bird species with distinct ecological needs. In contrast, the reserve consists of a relatively homogeneous xerophytic scrubland where a few species of shrubs and small trees are dominant. We also detected seasonal changes in five species, with highest occupancy during the warm-dry season of each year, which coincides with both their breeding season and the driest period of the year. This finding indicates that these birds find in the reserve and surrounding urban areas enough food and water during this limiting season as well as safe nesting sites. Our study provides evidence that some native birds can become urban exploiters and that the benefits that they obtain from urban settings are greatest during their breeding season.