Compared with the rest of Mexico’s, the avifauna of Baja California has been studied extensively (e.g., Grinnell 1928, Wilbur 1987). Nevertheless, within Baja California certain areas such as the Río Colorado delta have not been explored in detail. Knowledge of the bird life in this area is particularly important because of the striking changes in bird habitat along the Río Colorado and in its delta area (see Leopold 1970).