The seasonal abundance of Neartic shorebirds in the Gulf of Maranhão, Brazil, was studied by censusing three sites from April 1991–March 1992. Censusing was conducted on Cajual Island and Panaquatira Beach at 15-d intervals and at 30-d intervals on Raposa Beach. Bird movements were analyzed by comparing census data from the Gulf of Maranhão with those presented by McNeil (1970) for northeastern Venezuela and by Spaans (1978) for Surinam. During fall migration, there were marked similarities in the abundance peaks of Short-billed Dowitchers (Limnodromus griseus) and Willets (Catoptrophorus semipalmatus) in both Surinam and the Gulf of Maranhão, which might indicate that these species reach these sites by non-stop flight across the Atlantic. Sanderlings (Calidris alba), Semipalmated Plovers (Charadrius semipalmatus), Ruddy Turnstones (Arenaria interpres), Black-bellied Plovers (Pluvialis squatarola), Semipalmated Sandpipers (Calidris pusilla), and Whimbrels (Numenius phaeopus) reached their fall peak much later in Maranhão than in Surinam, which suggests that these species reach the Guyana coast first, migrating later to the Gulf of Maranhão. During northward migration, Willets and Whimbrels did not show a spring migration peak in the Gulf of Maranhão, whereas a spring migration peak was recorded in Surinam, which suggests a route to the Guyana coast and from there across the Atlantic Ocean to North America. Red Knots (Calidris canutus), Sanderlings, Ruddy Turnstones and Black-bellied Plovers all had spring migration peaks in the Gulf of Maranhão, suggesting some transoceanic flight of these species from the Maranhão coast to North America. Semipalmated Plovers and Short-billed Dowitchers showed a small spring migration peak in the Gulf of Maranhão, whereas no migration peak was observed for Semipalmated Sandpiper. This suggests that these species start their movements towards the northernmost portion of South America earlier.
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Vol. 71 • No. 4