The vireos make up a family, Vireonidae, of small to medium-sized passerine birds (mostly) restricted to the New World. They are typically dull-plumaged and greenish in color, the smaller species resembling wood warblers apart from their heavier bills. They range in size from the Chocó vireo, dwarf vireo and lesser greenlet, all at around 10 centimeters and 8 grams, to the peppershrikes and shrike-vireos at up to 17 centimeters and 40 grams (Forshaw & Parkes 1991).

The vireos make up a family, Vireonidae, of small to medium-sized passerine birds (mostly) restricted to the New World. They are typically dull-plumaged and greenish in color, the smaller species resembling wood warblers apart from their heavier bills. They range in size from the Chocó vireo, dwarf vireo and lesser greenlet, all at around 10 centimeters and 8 grams, to the peppershrikes and shrike-vireos at up to 17 centimeters and 40 grams (Forshaw & Parkes 1991).