Diverging roles of natural and artificial lagoons in supporting shorebird communities in the Gulf of Mannar, southeast coast of India

Coastal lagoons are vital habitats for migratory and resident shorebirds and are threatened by anthropogenic disturbance and environmental variability. Artificial wetlands such as salt pans serve as alternative habitats; hence, assessing their ecological equivalence to natural systems is essential. This study investigates the influence of temporal variation and rainfall on shorebird diversity and abundance in a natural lagoon (Dhanushkodi) and an artificial lagoon (Valinokkam) along the Gulf of Mannar, southeast India, over three years (2021–2024). Rainfall-induced habitat changes significantly shape shorebird communities, with natural lagoons displaying higher sensitivity to precipitation. In Dhanushkodi, species diversity increased with rainfall, while overall abundance declined. In contrast, the artificial lagoon at Valinokkam maintained relatively stable shorebird populations, likely due to consistent water levels. Rare species, including Red Knot Calidris canutus, Spotted Redshank Tringa erythropus, and Broad-billed Sandpiper Calidris falcinellus were recorded exclusively at Dhanushkodi. Five generalist species (Siberian Sand Plover Charadrius mongolus, Little Stint Calidris minuta, Curlew Sandpiper Calidris ferruginea, Kentish Plover Charadrius alexandrinus, and Greater Sand Plover Charadrius leschenaultii) accounted for 75% of total abundance in both lagoons. While artificial wetlands provide valuable alternative habitats for generalist shorebirds, they fall short in replicating the ecological complexity and dynamic processes of natural lagoons, particularly for species reliant on tidal flats. Anthropogenic threats influence shorebird behaviour and habitat use, with tourism and pollution being more pronounced in Dhanushkodi. These findings underscore the irreplaceable role of natural lagoons in sustaining shorebird diversity and highlight the need for targeted conservation strategies that consider site-specific ecological dynamics.