Urbanization and the temporal homogenization of bird communities: a case study in central Argentina

Urban expansion to rural and natural areas is a global process. Although several studies have analyzed bird community attributes along urbanization gradients, little is known on the impact of urbanization on temporal variability of bird communities. Rural areas show higher seasonal and interannual variability in environmental conditions and resources than do urban areas. Our objectives are to determine how seasonal and interannual variability in bird assemblages change along an urban-rural gradient, and how interannual variability in bird assemblages changes with season. Low seasonal and interannual variability of bird communities is expected in urbanized areas that show a process of temporal homogenization. Seasonal variability of bird richness and abundance were positively related to the percent cover of crops. Seasonal and interannual variability in community composition were positively related to coverage of herbaceous vegetation and crops, and negatively related to coverage of impervious areas. Interannual variability of bird richness and abundance were highest during the non-breeding season. We conclude that highly urbanized areas allow bird communities to have a more stable composition over time, promoting temporal homogenization. Our results emphasize that urbanization alters the temporal dynamics of resources and, therefore, the temporal variability of bird communities.