A local count with global consequences
On the southern coast of Sri Lanka, the brackish lagoons and mangrove forests of Kalametiya Bird Sanctuary are a critical data-gathering point for global ornithology. Since the 1980s, systematic and long-term wader censuses conducted here have provided hard numbers for a disturbing trend: the rapid decline of migratory shorebird populations. This small sanctuary's data was a significant piece of evidence in identifying a massive conservation crisis along the entire East Asian-Australasian Flyway (EAAF).
The EAAF is one of the world's nine major migratory waterbird flyways. It stretches from breeding grounds in Arctic Siberia and Alaska, south through East and Southeast Asia, to non-breeding grounds in Australia and New Zealand. The flyway supports over 50 million waterbirds, and is the world's most threatened, with overall waterbird species declining by 61%. Shorebirds are particularly affected. For species that rely heavily on the Yellow Sea mudflats for refueling, populations have been declining at an average rate of 5.2% per year. The primary threats are habitat loss from coastal development and reclamation, particularly at critical stopover sites in the Yellow Sea, where up to 400,000 hectares of intertidal mudflats are lost each decade.
The data from the mudflats
The bird counts at Kalametiya, often coordinated by organizations like the Field Ornithology Group of Sri Lanka (FOGSL), provide a southern anchor point for understanding the health of the flyway. FOGSL, Sri Lanka's affiliate of BirdLife International, has been instrumental in organizing bird counts and research since its founding in 1976. The data from these counts feeds into a larger, flyway-wide picture, allowing scientists to track population changes in specific species over decades.
One such species is the Curlew Sandpiper (Calidris ferruginea). This wader breeds in Arctic Siberia and migrates south, with a significant portion of its population wintering in Australia. Censuses across Australia have documented a severe population decline of over 77% in three generations (approximately 23 years). In some regions, the decline has been as high as 80% over two decades. Data from sites like Kalametiya are essential for monitoring these birds at their wintering grounds and stopover points, confirming the severity of the population crash. This has led to the Curlew Sandpiper's conservation status being uplisted to Critically Endangered in Australia. The consistent, long-term nature of the Kalametiya census makes its contribution to this global conservation effort indispensable.