The warbling vireo (Vireo gilvus) is a small North American songbird.
Its breeding habitat is open deciduous and mixed woods from Alaska to Mexico. It often nests in widely spaced trees, often cottonwood or aspen, along streams or rivers. It migrates to Mexico and Central America.
Measurements:
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 song is a cheerful warble, similar to that of the painted bunting and the purple finch. There are subtle differences in song between eastern and western birds, at least where the ranges meet in Alberta. Some authors recommend splitting the eastern and western subspecies of this species into separate species:
The brown-capped vireo (Vireo leucophrys), resident in Central America and northern South America, is sometimes considered conspecific with the warbling vireo.