Mercury contamination: A hidden threat to long distance migrant shorebirds in critical wintering sites on the West Coast of India

Important one of the many hypotheses attributed to the global decline in shorebirds is the exposure to contaminants, particularly concerning wintering shorebirds. However, there is limited information available on contaminant levels in winter migrant shorebirds, especially within the Central Asian Flyway. This research gap is addressed in this study on mercury contamination in 10 species of long-distance migrant shorebirds along the west coast of India from 2019 to 2021. Of all the 10 species of shorebirds studied, the highest concentration of mercury was reported in the droppings of Common Redshank in the mangroves (81.29 ± 6.82 mg/kg wet wt.) and the lowest was reported in Little Stint in sand beach (17.40 ± 2.14 mg/kg wet wt.). Kadalundi-Vallikunnu Community Reserve (KVCR) and its adjacent sand beaches serve as vital stop-over sites within the Central Asian Flyway, catering to the nutritional needs of various migratory shorebirds, including transoceanic, over-summering and locally moving species. This research offers solid evidence of mercury concentration in the predators occupying high trophic levels of the coastal ecosystems in the KVCR and surrounding areas. Understanding the extent and impact of mercury concentration on both organisms and their habitat is crucial. The study highlights a significant increase of Hg concentration across the years. Additionally, it provides essential information to support extensive, long term biomonitoring efforts aimed at conserving shorebirds regionally and globally.