Early in this century, Leopold (1949) described the Colorado River delta as a wild majestic paradise for wildlife. Since Leopold’s day, the river has been broken up by dams to sustain agricultural and urban development. Despite the area’s previous importance to wildlife, little research has been done there. We know of only a few old works on the ornithology of the area (Murphy 1917, Price 1899, Stone and Rhoads 1905). Therefore, from 0940 to 1200 on 5 June 1991 we made a preliminary reconnaissance of the birds of Montague Island, in the Colorado Delta, Baja California (Figure 1). We focused our effort on Estero del Chayo, a channel cutting into the southern part of Isla Montague. The island is formed by river sediment and has a simple vegetation consisting of saltgrass (Distichlis palmeri) on the banks adjacent to the channels of the estero. Away from the channels, unvegetated dry mudflats dominate. There is an extensive mudflat south of the island.