Although the Black Skimmer, Rynchops niger, is a familiar bird along the Pacific coast of mainland Mexico and southern California (AOU 1983), little is known of its occurrence on the peninsula of Baja California. Black Skimmers were not reported from Baja California until 1979 (Wilbur 1987) but now are observed regularly in winter along the northwestern coast (Wilbur 1987, Escofet et al. 1988). This colonial waterbird has recently established nesting colonies at San Diego Bay, in 1976 (McCaskie 1976, Unitt 1984), and at Bolsa Chica, Orange County, in 1985 (C. T. Collins, pers. comm.), so nesting is likely also in Baja California. In this area, Wilbur’s supportive records, mostly for winter, are from only three locations (near Maneadero, Bahía de San Quintín, and Isla San Martín) and of between two and 44 individuals.