(F. Mexicanus) inhabits the western United States from the eastern border of the Great Plains to the Pacific, and from the northern boundary southward into Mexico. It is a bird from seventeen to twenty inches long, the adult being pale grayish brown above, indistinctly but broadly barred with pale clay-color or bluish gray, while the lower parts are white, with the flanks heavily spotted or blotched with dusky. “The flight of this bird,” says Fisher, “is swift and graceful, though in most cases it is carried on at no great distance from the ground. It is not a shy bird, except in sections where it has learned that man is its worst enemy.” It is a typical plains bird and is found in the dry interior. The nest is usually placed on a shelf or niche in the perpendicular surface of a stream bank, a rocky ledge, or occasionally in hollow trees. They lay three or rarely four eggs, which are creamy white with blotches and spots of reddish brown. The Prairie Falcon feeds on birds, mammals, reptiles, and the larger insects, and does considerable damage in the way of destroying game birds, though this is perhaps more than offset by its destruction of injurious rodents.