Vireo is a genus of small passerine birds restricted to the New World. Vireos typically have dull greenish plumage (hence the name, from Latin virere, "to be green"), but some are brown or gray on the back and some have bright yellow underparts. They resemble wood warblers apart from their slightly larger size and heavier bills, which in most species have a very small hook at the tip. The legs are stout. Sexes are alike in all species except for the black-capped vireo, in which the male's crown is black and the female's is gray.