Warbling Vireo
At the height of breeding season, male Warbling Vireos sing their cheerful, buzzy song almost continuously. Warbling Vireos have even been observed singing while on the nest incubating eggs.

Warbling Vireos range from southern Alaska and northern Canada to central Mexico. They are widespread in suitable habitat in the western part of their range, but in the East they tend to be local, ranging from southern Ontario and Quebec to the highlands of Tennessee and North Carolina. They winter from Mexico to Costa Rica. Migration is chiefly at night, with eastern birds reaching the wintering grounds by way of Texas, rather than by flying across the Gulf of Mexico.
Warbling Vireo Range Map

In the eastern part of their range, Warbling Vireos nest high in the tops of trees, 40 feet up or more. Nests are typically suspended from a fork in one of the upper branches of a tall tree. Warbling Vireos favor deciduous trees such as aspens and poplars and are often found along watercourses. In the 1800s they were a common bird in cities, nesting on the Boston Commons, and in the early part of the 20th century, these vireos nested on the tree-lined streets of other New England cities. These urban populations declined, however, when shade trees were sprayed with pesticides.

In the West, Warbling Vireos are found in deciduous trees in canyons, along rivers, in prairie aspen groves, in clearings, and along woods’ edges in the mountains and in towns. Western birds tend to nest at lower heights than their eastern counterparts, often in low trees or shrubs within 30 feet of the ground.

A bird with few obvious field marks, Warbling Vireos are most easily detected by their song, which is unlike the songs of the other familiar eastern vireos. This song does not consist of short phrases given at long intervals; rather, it is truly a warble, reminiscent of the song of the Purple Finch. The song consists of a long, undulating series of deliberately delivered notes, no consecutive notes being the same. Individual Warbling Vireos typically sing between three and seven different variations, but a common format is a long note followed by two short ones, with the phrase ending on a high note. The phrase brig-adier, brig-adier, brig-adier, brigate suggests the rhythm. Warbling Vireos sing well into late summer, and even as late as September occasional songs are heard.

Description: Warbling Vireos are small songbirds (approximately 5.5 inches in length) with short, blunt-tipped bills. They are gray to olive-gray above with darker wings and tail and white underparts. There is a white superciliary line above the brown eye and a faint line through the eye. Compared to the very similar Philadelphia Vireo (V. philadelphicus), and the more distinctly marked Red-eyed Vireo (V. olivaceus), the face of the Warbling Vireo is very plain. The lack of strong contrasting markings and the widening of the white superciliary behind the eye give the Warbling Vireo a wide-eyed look of innocence. In the fall, the plumage tends to have more greenish tones, and the flanks may have yellowish tones.

Western Warbling Vireos, especially those from the Pacific Coast, tend to be slightly smaller with darker caps and may have more fall color. Their song is slightly different as well-less musical and more abrupt. Some authorities consider eastern and western Warbling Vireos to be separate species. Distinguishing the two forms is very difficult.

Of the North American vireos without spectacles and wing bars, separating Warbling Vireos from Red-eyed Vireo and Black-whiskered Vireo (V.altiloquus) is straightforward. The latter two species are larger, with strongly contrasting white and black stripes through and above the eyes, and with olive backs. The more difficult identification challenge is separating Warbling and Philadelphia vireos. Warbling Vireos generally have a less-distinct ocular stripe, slightly longer tails, and a less-rounded head. Philadelphia Vireos usually have more yellow on the underparts, but fall-plumaged Warbling Vireos may have strong yellow tones. Philadelphia Vireos show more bright yellow at the lower throat and upper breast, whereas the yellow on Warbling Vireos is confined to the flanks.


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