Boreal Birds
300+ species, billions of birds rely on Canada's boreal forest as critical breeding grounds
© Dominic Sherony/Wikimedia Commons (CC 2.0)

Cassin's Vireo

Cassin's Vireo
Vireo cassinii
Perching Birds | Family: Vireos, Vireonidae

An estimated 7% of the species' North American breeding range lies within the Boreal Forest.

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Overview

The bird formerly known as the Solitary Vireo was recently split into three separate species by American ornithologists: Cassin's, Plumbeous, and Blue-headed Vireos. Cassin's Vireo occupies the westernmost part of the former Solitary Vireo's range.

Description

5-6" (13-15 cm). Very similar to both Blue-headed and Plumbeous Vireos, with plumage roughly intermediate between the two. Duller and grayer overall than Blue-headed but shares that species' yellow sides and flanks, olive back, white wing-bars, and bold white "spectacles."

Voice

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

Nesting

3-5 white eggs, lightly spotted with brown, in a pendant cup of bark strips and down, placed in a forked twig of a small forest tree.

Habitat

Coniferous and mixed forests.

Range/Migration

Breeds from British Columbia, and southwestern Alberta south to central Idaho and along the West Coast to southern California. Most leave the U.S. in the fall but a small number overwinter in southeastern Arizona.