Species Diversity and Functional Assemblages of Bird Fauna along the Riverine Habitats of Tiruchirappalli, India

Riverine ecosystems have complex relationship with human since time immemorial and play an integral role in the socio-economy of a region. However, many riverine habitats, particularly within urban centers in the developing countries are subjected to overexploitation that affects the natural ecological processes and functions of rivers. Such perturbations in riverine habitats are often linked to biodiversity loss. Birds discharge crucial ecosystem services and are closely associated to wetlands and rivers for their survival. This study attempts to document the bird diversity and their community assemblages along the riverine habitats in relation to urban effects, vegetative attributes, seasonal parameters and other anthropogenic pressures. The study finds that bird diversity and species richness were higher in the rural landscape and gradually decreased towards the urban region. A total of 120 bird species consisting of two ‘Near Threatened’ were recorded along the riverine habitats of the River Cauvery. Few species (Egretta garzetta and Phalacrocorax niger), were found to be densely populated and adapted to the urban environment while few others declined. Salient features of the results include: seasonality did not affect the variability of the riverine species and the difference in composition of birds during the wet and dry seasons were insignificant. While the factors namely, tree cover, tree height, and number of trees were found to be positively correlated, the anthropogenic factors namely, extent of built up land, noise levels and vehicular traffic contributed negatively towards bird diversity. Among the various riverine stretches/study sites, the Kallanni region recorded highest species richness and diversity. The most important conservation measure would be to declare Kallanai an important bird reserve and the agricultural farmlands on either sides of river Cauvery at Kallanai be declared as ‘High Nature Value’ (HNV) wetlands/farmlands to protect the overall biodiversity.