Diversity and structure of bird assemblages along urban-rural gradient in Kolkata, India

Abstract

This study examined the bird assemblages by comparing the bird species diversity, composition, guild structure, and habitat and height utilization along the urban-rural gradient. Birds were surveyed from January 2008 to December 2009 using fixed-radius point counts in 20 sampling points randomly selected within four different habitat. A total of 134 species were recorded from 160 point count sampling plots. Of all the species recorded, 37 (28%) were found in all habitats and 35 (26%) found exclusively in some of the habitats. Out of 35 exclusive species, 30 (22%) were found in rural and semi-rural habitat, 5 (4%) were found in urban parks, and no exclusive species were found in high-density residential habitat. The species and guild composition in rural natural sites showed dissimilar assemblages in comparison to other habitat types, for example, the decline of insectivorous birds in response to increasing urbanization. The observed differences in bird assemblages reflect the differential availability of resources along the urbanization gradient. The results of this study support to the hypothesis that avian species richness or diversity failing to respond to urbanization linearly, but instead peaks at a level of intermediate disturbance or development.