Their locations as revealed by the Missouri Breeding Bird Atlas Project are shown on the following map. The warbler's winter habitat is concentrated on the eastern slopes of the Andes Mountains in western South America. Winter habitat is mature deciduous forest with large trees, usually at elevations of 10,000 to 13,000 feet. Once one of the most abundant breeding birds in the lower Mississippi valley, the cerulean warbler population is a fraction of its original size. This decline primarily followed logging in the early part of this century.
Recent surveys indicate there is a continued downward trend.
Range expansion may be due to land use changes. Areas that were logged heavily in the past are now being reforested and are attractive to cerulean warblers. Cerulean warblers are most abundant in the central and southern states of Pennsylvania, Maryland, Virginia, and West Virginia, where populations are stable. In Missouri, and throughout much of North America, loss of bottomland forest acreage has reduced cerulean warbler populations. On the South American wintering ground, removal of forest for coffee plantations has apparently resulted in less habitat, especially in the coffee-growing region of the northern Andes.