The vireo (Vireonidae) is a family of small, basically olive green, insectivorous and partly frugivorous songbirds with repetitive, persistent songs (sometimes musical, often harsh). The 52 known species, restricted to the New World, are related to the cosmopolitan shrike and crow.

Vireos spread northward from the American tropics, 8 species reaching Canada. Seven of these breed here, excluding Bell's vireo (Vireo bellii), which occurs, rarely, in spring at Point Pelee, Ontario. The only permanent resident is Hutton's vireo (V. huttoni), which lives in broad-leaved coniferous forests in extreme southwestern BC.

The thicket-dwelling white-eyed vireo (V. griseus) breeds in extreme southern Ontario. The yellow-throated vireo (V. flavifrons) inhabits mixed forest from southeastern Québec to southwestern Ontario and occurs locally in southeastern Manitoba. Solitary vireos (V. solitarius) frequent the Boreal forest transcontinentally north to Fort Simpson, NWT. The abundant red-eyed vireo (V. olivaceus), of mixed forests, ranges across Canada to 64° north latitude in the Northwest Territories.

The Philadelphia vireo (V. philadelphicus), vocally similar to the red-eyed vireo, inhabits deciduous woodland from southwestern Newfoundland to central BC. The warbling vireo (V. gilvus) prefers deciduous woodland from southwestern Québec to the West Coast.

Vireos build distinctive, pensile nests in trees and shrubs, breeding May-July; clutches contain 3-5 eggs.