Redistribution of wintering bird communities after wetland loss in Purba Medinipur, West Bengal, India

Coastal wetlands in East Medinipur, West Bengal, support a rich assemblage of aquatic and migratory birds but remain understudied concerning localized habitat disturbance. This study aimed to assess long term population trends at the four locations and quantify how the collapse of Jagadishpur wetland in 2024 affected avian diversity and abundance at four aquatic and migratory birds’ areas: Kanaichatta, Tajpur, Ranichak, and Jagadishpur. From 2020 to 2024, point counts and line transects were conducted during the winter months (November to February), recording 55 species and computing species richness, Shannon’s diversity, Simpson’s dominance, Pielou’s evenness, and total abundance for each site and year. Two-way ANOVA revealed significant location × year effects on diversity indices (p < 0.01). At the same time, the Kruskal–Wallis test confirmed that Jagadishpur’s 2024 richness and abundance were markedly lower than at the other sites (p < 0.01). Mann–Kendall trend analysis detected a strong negative monotonic decline in Jagadishpur (τ = −0.90, p = 0.017) but no significant trends elsewhere. Following habitat loss in Jagadishpur in 2024, birds were redistributed to nearby birds’ areas, leading to 187% higher abundance at Kanaichatta, and 38% at Tajpur. However, two Jagadishpur wetland specific birds (Asian Openbill and Knob-billed Duck) were not observed in any of the other three wetlands. Indicator species analysis (ISA) was applied to explore changes in community composition and key species associations, which revealed that specialist species sharply declined at Jagadishpur, whilst generalist species, such as Little Egret and Red Wattled Lapwing, increased in dominance. These results demonstrate that abrupt wetland destruction can decimate local bird communities and temporarily boost adjacent populations via immigration, underscoring the need for habitat restoration, improved connectivity, and long-term monitoring to sustain regional avian diversity.