Seasonal occurrence and site use by shorebirds at Sonadia Island, Cox’s Bazar, Bangladesh

We studied shorebird phenology at Sonadia Island, Cox’s Bazar, Bangladesh between Oct 2009 and Mar 2010. Boat-based surveys were carried out with a special focus on Spoon-billed Sandpiper Eurynorhynchus pygmeus and other endangered, threatened or vulnerable shorebirds including Nordmann’s Greenshank Tringa guttifer, Eurasian Curlew Numenius arquata, Great Knot Calidris tenuirostris and Black-tailed Godwit Limosa limosa. An aggregate total of 12,710 shorebirds of 28 species were recorded in Oct 2009, Jan 2010 and Mar 2010 at seven sites on or close to Sonadia Island. Maximum numbers of shorebirds and of shorebird species were counted during northward migration in Mar 2010 (6,714 individuals of 26 species). In Oct 2009, the most abundant species were Lesser Sandplover Charadrius mongolus (22.5% of the total count), Curlew Sandpiper Calidris ferruginea (20.3%) and Greater Sandplover Charadrius leschenaultia (16%); in Jan 2010, Lesser Sandplover (36.2%), Great Knot Calidris tenuirostris (18.6%) and Greater Sandplover (19.0%); and in Mar 2010, Lesser Sandplover (11.0%), Greater Sandplover (9.4%) and Curlew Sandpiper (7.8%). However, in October and March the percentage of probably both sandplover species would have been greater because of the considerable numbers of unidentified sandplover species that were recorded. Two globally endangered species were recorded with maximum numbers of both in March 2010: 25 Spoon-billed Sandpipers (5–7% of the estimated world population of 350–500), and 28 Nordmann’s Greenshanks (3–6% of the estimated world population of 500–1,000). In the same month there were peak counts of 433 Great Knots, 70 Black-tailed Godwits and 120 Eurasian Curlews which are all categorized as  threatened or vulnerable by BirdLife International (BirdLife International 2011, Zöckler et al.2010). We identified the most important feeding and roosting grounds for Spoon-billed Sandpiper and Nordmann’s Greenshank as Kaladia, Belekardia and Hasher Char; these meet the 1% threshold criterion to qualify as a Ramsar Site. Sonadia Island also meets several Ramsar criteria for recognition as a Wetland of International Importance.