Range. - Western United States, chiefly west of the Rockies; breeding north to British Columbia, and wintering south of the United States.
Similar to the last but smaller (length 4.5 inches), and paler in color, fading to white on the throat. The habits of this species are like those of the eastern Chimney Swift, except that the majority of these species still continue to use hollow trees as nesting places. The eggs are just like those of the last bird.