NOT a great deal is known about many of the warblers, and comparatively little has been observed of this member of the very large family, comprising more than one hundred species. This specimen is also recognized by the name of the blue-winged swamp warbler. Its habitat is eastern United States, chiefly south of 40 degrees and west of the Alleghanies, north irregularly to Massachusetts and Michigan, and west to border of the great plains. In winter it lives in eastern Mexico and Guatemala.

It has been pointed out that the name of this bird is misleading, as the blue of the wing is dull and inconspicuous, and not blue at all in the sense in which this color distinction is applied to some other birds. When applied to the warblers, it simply means either a bluish-gray, or slate, which seems barely different from plain gray at a short distance.

In half-cleared fields which have grown up to sprouts, and in rich open woods in the bottom-lands, where the switch-cane forms a considerable proportion of the undergrowth, the blue-winged yellow warbler is one of the characteristic birds, says Ridgway. The male is a persistent singer during the breeding-season, and thus betrays his presence to the collector, who finds this, of all species, one of the easiest to procure. His song is very rude. The nest is built on the ground, among upright stalks, resting on a thick foundation of dry leaves. The eggs are four or five, white, with reddish dots. The food of the warbler consists almost wholly of spiders, larvae, and beetles, such as are found in bark, bud, or flower. The birds are usually seen consorting in pairs. The movements of this warbler are rather slow and leisurely, and, like a chickadee, it may sometimes be seen hanging head downward while searching for food.