Mercury Contamination Threatens Kentish Plover Populations in a key Conservation Reserve in the West Coast of India

Despite the profound toxicity of mercury (Hg) to shorebirds, the growing mercury contamination in India has received little attention regarding its impact on their population decline. As an indicator species facing both global and regional population declines, the Kentish Plover is ideal for monitoring shorebirds’ exposure to Hg within their habitats. Our study aimed to monitor Hg contamination in Kentish Plovers by documenting mercury concentrations in their droppings across two adjacent microhabitats—mudflats and mangroves— within Kadalundi-Vallikkunnu Community Reserve (KVCR). KVCR is a key conservation reserve on the west coast of India, witnessing a decline in the Kentish Plover population. Droppings were sampled in triplicates during November, December and January from 2019 to 2024. The findings revealed a significant rise in Hg levels in the droppings over the study period. In the mudflats, the average Hg concentration in the droppings increased significantly from 26.08 ± 0.11 mg/kg wet weight in 2019 to 65.39 ± 2.03 mg/kg ww in 2024 (F _(5,12) = 168.6; p < 0.01). Likewise, in the mangroves, the average Hg concentration rose significantly from 47.85 ± 2.46 mg/kg ww in 2019 to 73.12 ± 0.95 mg/kg ww in 2024 (F _(5,12) = 62.53; p < 0.01). Remarkably, the droppings of Kentish Plovers foraging at mangroves revealed highest loads of Hg (60.02 ± 9.64 mg/kg ww) than in those foraging at mudflats (47.85 ± 13.94 mg/kg ww), indicating a greater accumulation of Hg contaminants at mangroves microhabitats than at mudflats. From a conservation perspective, this study underscores the critical role of Hg contamination in the declining Kentish Plovers population within KVCR, emphasizing the urgent need for conservation efforts.