The family Vireonidae includes 16 species found in North America.

Vireos are small (10-17 cm, 9-24 gm). Plumages are mainly gray, greenish or brown above and whitish or yellowish below. Some species have white eyerings, white superciliary lines and/or white wing bars. The sexes are alike. Vireos inhabit broad-leaved or mixed forest and scrub. Food is mainly insects during the breeding season, with up to 50% fruit during migration and winter in Central and South America. They forage by taking insects from the foliage, sometimes by hovering at leaf clusters and some by the capture of flying insects on the wing. The Gray Vireo, which lives in the arid southwestern U.S. and northwestern Mexico, also forages on the ground.

Nests are deep cups of leaves, grass and bark strips, bound together with cobwebs and lined with fine grass. The nest is suspended by the rim from the fork of a small branch in foliage. Both sexes build in most species, only the female in some. Construction time is 5-15 days. Eggs 4-5, white and unmarked, or white with various degrees of brown spotting, usually concentrated at the large end. Incubation is 11-13 days beginning with the 2nd egg. Males of most species sing while incubating. Both sexes care for the young during the 12 day nestling period. Fledging is 30-40 days after hatching.