Guide to North American Birds

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Adult. Photo: Tim Zurowski/Shutterstock

Cassin's Vireo

Vireo cassinii

In the Pacific states and parts of the northern Rockies, this vireo is common in summer. When feeding, it works rather deliberately along branches, searching for insects. Its nest, suspended in the fork of a twig, is often easy to find. This bird was formerly lumped with the Blue-headed and Plumbeous vireos under the name Solitary Vireo.

Conservation status	Widespread and common, numbers apparently stable.
Family	Vireos
Habitat	Coniferous, deciduous, and mixed woods. Breeds in rather open woods. Often found in oaks near the coast, in ponderosa pines and Douglas-firs in the interior, but may be in mixed coniferous-deciduous woods anywhere. Migrants occur in any kind of woodland.

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Feeding Behavior

Forages rather deliberately in trees, searching for insects along branches and twigs as well as among leaves. Sometimes flies out to catch insects in mid-air, or searches for items on bark of major limbs.

Eggs

3-5, usually 4. Whitish, lightly spotted with brown. Incubation is by both parents, about 12-14 days. Nests are often parasitized by cowbirds. Young: Both parents feed the nestlings. Young leave the nest about 2 weeks after hatching.

Young

Both parents feed the nestlings. Young leave the nest about 2 weeks after hatching.

Diet

Mostly insects. In summer feeds almost entirely on insects. True bugs (including stink bugs, treehoppers, and leafhoppers) are major items in diet; so are caterpillars, beetles, wasps, bees, ants, and others; also spiders. May eat a few small fruits and berries in winter.

Nesting

Male sings frequently throughout the day to defend nesting territory. In courtship display, male may fluff up plumage and bob his body up and down. Nest: Placed in horizontal fork of branch in tree, usually near the tip, and often 15 to 20' above the ground. Nest (built by both sexes) is a rather bulky open cup, suspended by its rim. Nest is made of grass, strips of bark, rootlets, lined with fine grasses and plant fibers. Outside of nest may be decorated with moss, lichens, pieces of paper.

Illustration © David Allen Sibley.
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Text © Kenn Kaufman, adapted from
Lives of North American Birds

Migration

Tends to migrate early in spring and late in fall. Small numbers winter in the southwest.

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Migration

Tends to migrate early in spring and late in fall. Small numbers winter in the southwest.

All Seasons - Common
All Seasons - Uncommon
Breeding - Common
Breeding - Uncommon
Winter - Common
Winter - Uncommon
Migration - Common
Migration - Uncommon

Songs and Calls

Song a series of phrases; intermediate between clear notes of Blue-headed Vireo and rough, husky notes of Plumbeous Vireo. Call a husky chatter.

Audio © Lang Elliott, Bob McGuire, Kevin Colver, Martyn Stewart and others.
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How Climate Change Will Reshape the Range of the Cassin's Vireo

Audubon’s scientists have used 140 million bird observations and sophisticated climate models to project how climate change will affect this bird’s range in the future.

Zoom in to see how this species’s current range will shift, expand, and contract under increased global temperatures.

Climate Threats Near You

Climate threats facing the Cassin's 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.