The Warbling VireoVireo gilvus, is a small North American songbird. Its breeding habitat is open deciduous and mixed woods from Alaska to Mexico and the Florida Panhandle. It often nests along streams. It migrates to Mexico and Central America.
Adults are 4.7 inches long. They are mainly olive-grey on the head and upperparts with white underparts; they have brown eyes and the front of the face is light. There is a white supercilium. They have thick blue-grey legs and a stout bill. Western birds are generally smaller and have darker grey crowns.
Warbling Vireos forage for insects in trees, hopping along branches and sometimes hovering. They also eat berries, especially before migration and in winter quarters, where they are – like other vireos – apparently quite fond of Gumbo-limbo seeds, though they will not venture into human-modified habitat to get them.
They make a deep cup nest suspended from a tree branch or shrub, placed relatively high in the east and lower in the west. The male helps with incubation and may sing from the nest.
The Warbling Vireo's song is a cheerful warble, similar to that of the Painted Bunting. There are subtle differences in song between eastern and western birds, at least where the ranges meet in Alberta.