306 DOI:https://doi.org/10.52756/ijerr.2023.v30.028 Int. J. Exp. Res. Rev., Vol. 30: 306-320(2023) Diversity, Composition and Abundance of Avian Species of Oxbow Lake and Surrounding Area in Purbasthali, West Bengal, India Santanu Chowdhury Department of Environmental Science, Asutosh College, Kolkata, West Bengal, India E-mail/Orcid Id: SC, santanu.chowdhury@asutoshcollege.in, https://orcid.org/0009-0007-2524-5185 Introduction Biodiversity provides important information about the overall health of an ecosystem (Díaz et al., 2007; Dudgeon et al., 2006). Species richness and diversity in an ecosystem are greatly influenced by the availability and distribution of resources in a particular habitat (Baer et al., 2004; Silvertown, 2004). Lakes are one of the most important freshwater resources on Earth and supports huge biodiversity (Gibbs, 1993). Wetlands/lakes are highly complex as well as productive ecosystems which helps to maintain the ecological balance by providing various ecological services like aquaculture, ground water recharge, flood control, wastewater treatment, drinking water source, agricultural water use, soil erosion control, nutrient cycling, habitat for a wide range of plant and animals etc. (Joy et al., 2005; Bhatta et al., 2016). The structure of an aquatic body also determines the species composition, density and diversity of a particular ecosystem (Watson et al., 2004). It is considered to be the most important habitat for various types of migratory and residential avian species for their wintering and breeding grounds (Szabo et al., 2017). In recent times freshwater lake ecosystem in India are threatened by various anthropogenic activities like habitat loss and degradation, habitat fragmentation, encroachment or unlawful filling of aquatic habitat, pollution, overexploitation of resources, waste dumping, heavy metal contamination, contamination from municipal and agricultural sources etc. These leads to aquatic body degradation, threatening the species thrives on the aquatic ecosystem (Sreekumari et al., 2016; Bassi et al., 2014; Bhattacharya, 2014; Roy et al., 2022). Avian diversity is one of the most significant ecological factors determining the quality of aquatic ecosystems and acting as a bioindicator. Emerging threats of climate change, habitat loss, habitat fragmentation, over- extraction of resources and pollution raise new concerns over the degradation of aquatic ecosystems, which in turn threatens the existence of avian species diversity (Rahmani et al., 2022; Rajashekara et al., 2018). The oxbow lake at Article History: Received: 14 th Feb., 2023 Accepted:15 th Apr., 2023 Published:30 th Apr., 2023 Abstract: Purbasthali oxbow lake is an important habitat for thousands of migratory and resident avian species. This study aimed to determine the current status of avifaunal diversity of Purbasthali oxbow lake and its surrounding area. During this study, diversity, composition and abundance, feeding guilds and the relationship between their habitat preferences and the numbers of individuals were determined. Direct observation, line transects and point count methods were applied for bird surveys for three consecutive years from 2019 to 2022. A total of 145 species of birds were documented, belonging to 19 orders and 49 families. Among the total species, 57 are migratory in nature and 47 are showing declining global trend. Quantitative diversity estimation were performed during the study are the Shannon-Weiner index, Simpson's Diversity Index, Shannon equitability index and relative diversity. Density and diversity of avian species was highest during post-monsoon and lowest in pre monsoon. This indicates the winter assemblages of many migratory birds choose this lake as their feeding and resting grounds. Keywords: Avian diversity, Migratory birds, Oxbow lake, Shannon-Weiner index, Simpson's diversity index