The interaction of imperviousness and habitat heterogeneity drives bird richness patterns in south Asian cities

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.

Automated summary

By analyzing bird data from South Asian cities, this study found a significant impact of the interaction between habitat heterogeneity and human built-up extent on local bird species richness. The results suggest that high urbanized areas require increased habitat heterogeneity to maintain high levels of local bird diversity.