Abstract
ABSTRACT: Urbanization causes environment changes that directly affect biotic diversity, and understanding the relationship between fauna and urban features is a key aspect of urban planning. Birds are particularly affected by urbanization. Noise levels, for instance, negatively affect birds’ behavior and social communication, while the presence of green areas promotes bird diversity. The effects of urbanization could differ according with the level of urbanization, and our goal was to understand how bird species assemblages are related to urban features in an intermediate stage of urbanization (a city in Brazil with 2,470 inhabitants/km²). We used canonical correspondence analysis (CCA) and generalized linear models (GLM) analyses to assess how bird species assemblages are affected by urban features (e.g., noise level, abundance of buildings) as well as habitat features (e.g., vegetation cover). Despite we did not find a clear pattern of urbanization both the urban and habitat features had, even if weak, an effect on bird species distribution. Bird species distribution was spatially correlated, and we identified three groups: 1) grassland and wetland species; 2) forest species; 3) species tolerant to habitat degradation. Species richness was positively related to the proportion of trees, abundance of people and presence of buildings, and negatively affected by higher levels of noise. The abundance of species decreased as noise levels increased, but the proportion of green areas (open or forest vegetation) had a positive effect. Agreeing with previous research, our study shows that noise levels and vegetation cover seem to be the best predictors of diversity in urban areas. Nevertheless, the presence of particular habitats (wetlands, grasslands, woodlots), patchily distributed in the urban matrix, could buffer the effects of urbanization on birds. These habitats should thus be taken into account in urban planning.
Highlights
Urban ecosystems are complex, heterogenic and dynamic, characterized mainly by dense agglomerations of people living in the same place
High densities of human dwellings – and people – and high levels of noise are associated with lower levels of bird diversity (Evans et al, 2009; Fontana et al, 2011), but higher bird abundances (Evans et al, 2009). This pattern of continuous decline of diversity and increase in abundance is exhibited along the rural-urban gradient (Blair, 1996; Chace & Walsh, 2006; McKinney, 2006; Puga-Caballero et al, 2014; Bino et al, 2008; Ortega-Álvarez & MacGregorFors, 2011), diversity could peak at intermediate levels of disturbance, as in peri-urban areas (Blair, 1996, 2004; Tratalos et al, 2007)
We use features of the urban landscape to test the predictions that (1) the degree of urbanization affects bird species distribution, and intensely urbanized areas have lower species richness and higher species abundance than less urbanized areas; (2) both species richness and abundance diminished in proportion to noise level; (3) vegetation is an important component of the urban landscape for birds, and bird diversity will increase in proportion to the area of green space in the city
Summary
Heterogenic and dynamic, characterized mainly by dense agglomerations of people living in the same place. High densities of human dwellings – and people – and high levels of noise are associated with lower levels of bird diversity (Evans et al, 2009; Fontana et al, 2011), but higher bird abundances (Evans et al, 2009) This pattern of continuous decline of diversity and increase in abundance is exhibited along the rural-urban gradient (Blair, 1996; Chace & Walsh, 2006; McKinney, 2006; Puga-Caballero et al, 2014; Bino et al, 2008; Ortega-Álvarez & MacGregorFors, 2011), diversity could peak at intermediate levels of disturbance, as in peri-urban areas (Blair, 1996, 2004; Tratalos et al, 2007). We use features of the urban landscape to test the predictions that (1) the degree of urbanization affects bird species distribution, and intensely urbanized areas have lower species richness and higher species abundance than less urbanized areas; (2) both species richness and abundance diminished in proportion to noise level; (3) vegetation is an important component of the urban landscape for birds, and bird diversity will increase in proportion to the area of green space in the city (parks, gardens, orchards)
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