Temporal Patterns in Shorebird Diversity and Abundance at Dhanushkodi Lagoon: A Critical Wintering Ground along India’s Southeast Coast

Shorebirds are bioindicators of coastal wetlands, which act as crucial stopover and wintering sites. Temporal factors, such as seasonal variations, tidal cycles, and climatic conditions, influence the quality and resource availability, particularly food, roosting, and foraging habitats, for migratory and resident shorebirds. The present study was carried out in Dhanushkodi Lagoon, a significant wintering site along the Central Asian Flyway (from June 2017 to May 2024) using vantage point counts. Total 37 shorebird species were recorded, including 10 Near Threatened, three Vulnerable and two Endangered species and the endemic Hanuman Plover Charadrius seebohmi (Not Evaluated in IUCN). The lagoon harbored 86.4% of winter visitors during the study period, with Siberian Sand Plover (Charadrius mongolus, 20.3%), Curlew Sandpiper (Calidris ferruginea, 17.8%), Greater Sand Plover (Charadrius leschenaultii, 14.8%), Kentish Plover (Charadrius alexandrinus, 11.8%), and Little Stint (Calidris minuta, 10.9%) being the predominant species, which collectively contributed 75.5% to the temporal dissimilarities in species composition (SIMPER analysis). Shorebird abundance increased (57.18%) from 2021-22, following a notable decline (40.48%) between 2018-19 and 2020-21. The highest abundance was in 2023-24 (42012 individuals), with lower species diversity (H’ = 2.116) and richness (R = 0.150), whereas 2020-21 had the lowest shorebird abundance (14035 individuals) yet the highest diversity (H’ = 2.324) and richness (R = 0.236). Abundance increased in August and peaked (143.6%) in March and April during the northward migration, while June was the lowest. These findings highlight Dhanushkodi Lagoon’s significance, emphasizing the need for systematic conservation of this wetland.