ABUNDANCE AND SEASONAL-VARIATION OF WESTERN SANDPIPERS (CALIDRIS-MAURI) IN BAJA-CALIFORNIA-SUR, MEXICO

Northwestern Mexico is assumed to be one of the most important winteri ng areas for western sandpipers (Calidris maun). However, abundance ha s only been quantified recently via aerial surveys. In 1992 we censuse d Chametla beach within ensenada de La Paz, to quantify shorebirds' se asonal variation. The western sandpiper was the most numerous species during fall migration (late July to early November), and during the wi nter period (November to March) especially. In contrast to the eastern shore of the Gulf of California, we did not detect a spring migration increase, and assumed that the area is used exclusively for the fall migration and for wintering. There are two habitats available: marsh a nd mudflats. The latter was the more important for feeding. The distri bution of western sandpipers was constrained by seasonal tide levels a s more habitat is available during fall migration.