Responses of urban tolerant birds to the level of urbanization in a neotropical city

Abstract

This paper compares the proportion of urban tolerant birds in the urban avian community and the amount of built-up areas, mostly impervious surface, as indicators of urbanization on patterns of avian species composition in a Neotropical city in Southern Brazil. From September to December 2013 (breeding season), bird surveys were conducted in 120 squares of 100 ha randomly select within Curitiba. All bird species seen or heard during the sample timeframe was recorded.The extent of urban modification and disturbance was estimated directly from urban landscape data analyses through a geographic information system. Simple regressions were graphed and performed (Spearman rank correlations) to assess the relationship of overall species richness and the percentage of urban tolerant birds against the percentage of built-up areas as the predictor variable. Kruskal-Wallis non-parametric analyses of variance were performed to test if the total richness or the percentage of urban tolerant birds on the assemblages differed between different categories of urbanization (low, intermediate and high). We recorded 102 bird species, including 13 urban tolerant species. As expected, urbanization significantly reduced species richness, but urban tolerant species were less affected to changes on land modifications associated to urban growth. The increase representativeness of "urban-adaptable" species on the bird assemblages of intermediate and high urbanized areas in Curitiba was probably favored by their broad environmental tolerance. Most urban tolerant species registered are ground foraging resident birds, use a diverse array of anthropogenic resources, and can be found occupying various types of habitat in several human-modified ecosystems.