Annual patterns of abundance of Nearctic shorebirds and their prey at two estuarine sites in Ceará, NE Brazil, 2008–2009

This study, conducted between September 2008 and August 2009, documents species occurrence, annual abundance and prey of Nearctic-nesting shorebirds at two sites in NE Brazil: Ilha Grande and Cajuais Bank in the state of Ceará. At Ilha Grande, 14 shorebird species were recorded. The most abundant were Blackbellied Plover Pluvialis squatarola, Ruddy Turnstone Arenaria interpres, Whimbrel Numenius phaeopus, Semipalmated Plover Charadrius semipalmatus, Semipalmated Sandpiper Calidris pusilla, and Least Sandpiper C. minutilla. Highest numbers were found in April (1,805), and August (839). At Cajuais Bank, 15 species were recorded, the most abundant being Red Knot Calidris canutus, Short-billed Dowitcher Limnodromus griseus, Semipalmated Plover, Semipalmated Sandpiper, and Ruddy Turnstone. The highest numbers were found in September (1,539) and December (1,609). In April 2009, 2,000 Red Knots were recorded on a beach near Cajuais Bank. Hitherto, no data on significant numbers of Red Knots spending the non-breeding season on the semi-arid coastline of NE Brazil have been reported.

Fiddler-crabs were the main prey of Whimbrels, Ruddy Turnstones, and Blackbellied Plovers at Ilha Grande. At Cajuais Bank, mollusc- and polychaete-eating shorebirds predominated. The most frequent prey in Red Knot and Short-billed Dowitcher droppings were Tellinidae and Donacidae clams and Nereis polychaetes, respectively. Ruddy Turnstones were observed preying on Tivela and Anomalocardia clams and Cardium cockles. Urgent attention should be given to the coastal habitat of Ceará and neighboring Rio Grande do Norte, since this is a semi-arid coastline with fragile hypersaline estuaries. The increasing loss of coastal habitats may create a ca.1,000 km-long gap in suitable areas for migratory shorebirds in the West Atlantic Flyway.