Cassin’s Vireo
Cassin's Vireo
Vireo cassinii
At a Glance
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.
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
Forests and Woodlands
Region
California, Northwest, Plains, Rocky Mountains, Southwest, Western Canada
Behavior
Direct Flight, Flitter, Rapid Wingbeats
Population
5.000.000
Range & Identification
Migration & Range Maps
Tends to migrate early in spring and late in fall. Small numbers winter in the southwest.
Description
5-6" (13-15 cm). Like a duller version of Blue-headed Vireo; best separated by range. Where they overlap, some may not be identifiable. Plumbeous Vireo is more purely gray, slightly larger, less active. Cassin's often flicks its wings nervously, like Hutton's Vireo.
Size
About the size of a Sparrow
Color
Black, Brown, Gray, Green, White, Yellow
Wing Shape
Pointed
Tail Shape
Notched, Square-tipped
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.
Call Pattern
Flat, Undulating
Call Type
Buzz, Chirp/Chip, Whistle
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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Behavior
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.
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.
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.
Climate Vulnerability
Conservation Status
Widespread and common, numbers apparently stable.
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.