Western Warbling Vireo
Western Warbling Vireo
Vireo swainsoni
At a Glance
Rather plain, but with a cheery song, the Western Warbling Vireo is a common summer bird in open woods and leafy riverside groves. A persistent singer, it lives up to its name by continuing to give its unhurried, warbled song even on hot summer days when most birds have fallen silent. Until 2025, this bird and the Eastern Warbling Vireo were considered a single species. The differences between them are very subtle, and the safest way to tell them apart is by range.
All bird guide text and rangemaps adapted from Lives of North American Birds by Kenn Kaufman© 1996, used by permission of Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Category
Perching Birds, Vireos
IUCN Status
Least Concern
Habitat
Arroyos and Canyons, Forests and Woodlands, High Mountains, Shrublands, Savannas, and Thickets
Region
Alaska and The North, California, Northwest, Plains, Rocky Mountains, Southwest, Texas, Western Canada
Behavior
Direct Flight, Flitter, Rapid Wingbeats
Population
53.000.000
Range & Identification
Migration & Range Maps
Migrates mostly at night. The Western Warbling Vireo spends the winter in western and southern Mexico, with a few as far south as Guatemala. On breeding grounds in northern California, recent decades have shown a trend toward earlier arrival in the spring.
Description
Sexes similar — Length: 4.7–6 in (12–15 cm); wingspan: data unavailable; weight: 0.3–0.6 oz (10–16 g). The Western Warbling Vireo is gray and white, sometimes with yellow and olive tinges, especially when in fresh plumage. No wing-bars. On the Western Warbling Vireo, the white eyebrow is obvious, but the darker line through the eye is faint, so the dark eye is conspicuous on the pale face. The Eastern Warbling Vireo is almost identical but tends to have a slightly thicker and paler bill, a shorter white eyebrow, and a paler crown. The songs of the two species differ slightly. Also see Tennessee Warbler.
Size
About the size of a Sparrow
Color
Black, Gray, White, Yellow
Wing Shape
Rounded
Tail Shape
Notched, Square-tipped
Songs and Calls
The song of the Western Warbling Vireo is a drowsy, rambling warble, rising and falling in pitch, with some rough or burry notes thrown in. The song of the Eastern Warbling Vireo tends to be a little longer, with fewer rough notes, and usually ends on a rising note.
Call Pattern
Falling, Flat, Undulating
Call Type
Buzz, Chirp/Chip, Hi, High, Whistle
Habitat
Deciduous and mixed woods, aspen groves, poplars, shade trees. The Western Warbling Vireo breeds in open deciduous or mixed woodland, or in deciduous groves within coniferous forest; also in canyons, prairie groves, orchards, and shade trees of towns. Winters in the tropics in open woods.
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Behavior
Eggs
4, sometimes 1- 5. White with brown or black specks. Incubation is by both parents, 12-14 days. Male Western Warbling Vireos frequently sing from the nest while incubating. Commonly parasitized by Brown-headed Cowbirds.
Young
Nestlings are fed and brooded by both parents, leave the nest 12-16 days after hatching.
Feeding Behavior
Forages mostly in deciduous trees, sometimes in shrubs, hopping along twigs and searching for insects among the leaves. The Western Warbling Vireo also picks insects off the undersides of leaves while hovering briefly.
Diet
Mostly insects, some berries. During the breeding season, the Western Warbling Vireo feeds mainly on insects, including many caterpillars, aphids, beetles, grasshoppers, ants, bugs, scale insects, flies, and dragonflies; it also eats some spiders and snails. Takes berries and small fruit from dogwood, pokeweed, sumac, elderberry, and many other plants, especially in late summer and fall.
Nesting
Male defends territory by singing. In courtship, the male Western Warbling Vireo struts and hops around the female with his wings spread and tail fanned, usually not far from the potential nest site. Nest is generally in a deciduous tree or shrub, sometimes high but often within 30 ft of ground. Nest (built by both sexes) is a compact, deep cup, suspended by its rim from a forked twig. Nest made of bark strips, grass, leaves, and plant fibers.
Conservation
Conservation Status
Common and widespread. Some populations of Western Warbling Vireo in California may be declining, but numbers elsewhere in the West appear to be increasing.
Climate Threats Facing the Western Warbling Vireo
Choose a temperature scenario below to see which threats will affect this species as warming increases. The same climate change-driven threats that put birds at risk will affect other wildlife and people, too.
