<p>Understanding long-term changes in shorebird populations is crucial for assessing the ecological health of coastal habitats. We present a four-decade (1985–2024) assessment of shorebird abundance and community composition across key sites in the Gulf of Mannar, India, based on four non-continuous survey periods (1985–1988, 2005–2007, 2018–2019 and 2021–2024). A total of 40 species were recorded. Standardised peak seasonal counts analysed using a hierarchical generalised linear mixed model (GLMM) indicate a ~ 57% decline in overall abundance, with a marked reduction after 1987–1988. Segmented trend analysis identified breakpoints in 1987–1988 and 2021–2022, suggesting shifts in population trajectories. Historically abundant species, including Siberian Sand Plover and Curlew Sandpiper, declined significantly, whereas Kentish Plover and Greater Sand Plover increased in recent years. Species turnover was high (29.7%), with the notable addition of the recently recognised Hanuman Plover. Community analyses (NMDS, PERMANOVA) revealed significant temporal restructuring across all sites and repeatedly surveyed sites. In contrast, GLMM-based estimates of abundance showed a larger decline (~ 70%) when restricted to repeated sites, indicating that anthropogenic wetland Valinokkam may act as a supplementary habitat in increasing recent abundance, not as a driver of the entire community shift over decades. These patterns are likely associated with habitat modification and increasing anthropogenic pressures. Despite methodological constraints, this pioneering study provides one of the few multi-decadal assessments from the Central Asian Flyway and underscores the need for standardised monitoring and targeted coastal conservation strategies.</p>