Abstract
Bird species richness has often been used as an indicator of urbanisation effects on biodiversity in North America and Europe, but similar studies are rare in rapidly urbanising regions in the tropics. Here we assess the effect of different urban environmental factors on local resident bird species richness at different spatial extents in South Asian cities. Bird data at 57 urban locations distributed across 11 cities were retrieved from the available literature. Different variables assessing the degree of urbanisation and urban habitat factors were measured, at 1000 m and 5000 m radius scale extent, for each urban location. We investigated how resident bird species richness was affected by urban environmental predictors by fitting linear regression models in a Bayesian framework. Our model suggested strong positive influence of the interaction between habitat Shannon metric (a proxy of habitat heterogeneity) and proportion of impervious surface (a proxy of human built-up and settlement extent) on local resident bird richness at both spatial scales. Increasing values of habitat Shannon metric positively related to increasing bird richness, but only when the proportion of impervious surface was very high. Our results suggest that areas with a high degree of urbanisation necessitate an increase of habitat heterogeneity to maintain high local bird diversity. Increasing the quality and the compositional variability of remaining bird habitat patches in highly built-up areas should be a major conservation concern within cities of South Asia.
Highlights
Natural and near-natural ecosystems are globally changing toward man-made urban ecosystems, with increasing interaction between human and natural systems (Kareiva et al 2007; Strohbach et al 2014)
Our study provides the first comparative assessment of bird species richness drivers across several urban localities distributed at different cities of South Asian cities and offer insights into the processes underpinning bird species richness in a tropical region, partially filling a geographical gap
Our results show that the interaction of imperviousness and habitat heterogeneity is the main driver of bird species richness within South Asian cities, supporting the argument that anthropogenic effects shape bird diversity within cities (Evans et al 2009; Aronson et al 2014)
Summary
Natural and near-natural ecosystems are globally changing toward man-made urban ecosystems, with increasing interaction between human and natural systems (Kareiva et al 2007; Strohbach et al 2014). Green spots are shrinking, and native vegetation within city parks is often replaced with exotic plants (Chace and Walsh 2006; Sjöman et al 2012). These changes are of conservation concern, as they may cause a decline of native bird species in urban sites (Chace and Walsh 2006). Urban ecologists have repeatedly stressed the importance of maintaining an intermediate degree of urbanisation for the conservation of birds and overall
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