Waterbird Assemblage Structure, Seasonal Dynamics and Anthropogenic Pressures in Sengulam Lake, An Urban Wetland of the Noyyal River Basin, South India

Urban wetlands are increasingly threatened by pollution, habitat modification, and unregulated human activities, despite supporting significant avifaunal diversity. This study assessed the waterbird assemblage structure and anthropogenic pressures in Sengulam Lake, an urban wetland in Coimbatore within the Noyyal River basin, south India (March 2025 to February 2026), using vantage point count method. A total of 151 avian species belonging to 19 orders and 56 families were recorded. Passeriformes was the dominant order (57 species), while Ardeidae was the dominant family (11 species). The resident species predominated (110 species), followed by winter visitors (36 species) and local migrants (5 species). The assemblage was largely composed of Least Concern species (148 species), with two Near Threatened species - Indian Roller Coracias benghalensis and Asian Woollyneck Ciconia episcopus, and one Vulnerable species River Tern Sterna aurantia. Carnivorous and omnivorous birds formed the dominant feeding guilds throughout the study period. Species richness (119 species) and abundance (1676 individuals) were the highest in December. Shannon diversity remained consistently high (3.16–3.80), with low Simpson’s dominance values (0.038–0.090), indicating the absence of strong dominance by any single species. Temporal beta diversity (βSOR = 0.634) was mainly driven by species turnover (βSIM = 0.476). Major threats were sewage inflow, solid waste dumping, water hyacinth invasion, recreational disturbance, stray dogs, and habitat alteration. These pressures affected multiple avifaunal guilds through habitat degradation, altered foraging behaviour, and displacement. The study highlights the need for sewage management, invasive species control, and shoreline protection, thereby emphasising the conservation importance of Sengulam-Lake.