Slate-gray above; white below; dark gray to black tail with white on the outer feathers on each side; wings charcoal colored; white eye ring; the tail from below appears almost all white when folded. 11 cm (4.5 in) in length.
The breeding season begins in mid-April, peaks in May, and extends to early June. The breeding habitat encompasses many types of forested areas, including deciduous forest, wooded areas, and bottomland forest. The nest is commonly built 2-25 feet ( m) above the ground in a tree. The cup-shaped nest is built by both adults out of lichen, spider webs, and plant material. The female lays 4-5 eggs that both adults incubate for approximately 13 days. The young are alticial and fledge 10-12 days after they hatch. Both adults brood the young at the nest.
Non-breeding habitats are usually forested habitats or thickets. The diet of the Blue-gray Gnatcatcher is primarily insects that it captures by searching among the leaves. Some individuals of this species are long-distance migrants.
The Blue-gray Gnatcatcher occurs throughout most of the eastern and southwestern United States during the breeding season. It occurs in the coastal Southeast all year. Wintering birds are seen from the southern United States south to Central America. These gnatcatchers are found throughout Georgia during the breeding season, but during the winter they are seen mostly in the southeastern portion of the state.
This species is common throughout its southeastern range. Fairly often, it plays host to the Brown-headed Cowbird, which parasitizes its nest so that the gnatcatchers raise cowbird young instead of their own.
The Blue-gray Gnatcatcher is the only species of gnatcatcher common in the eastern United States. The closest common species is the southwestern Black-tailed Gnatcatcher, which is much darker overall, with a dark gray to black head, and much less white on the tail than the Blue-gray Gnatcatcher has.