Cassin's Vireo

Cassin's Vireo

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1. Description
2. Sound
3. Conservation Status
4. Other Names
5. Cool Facts
6. Full detailed species account

A common bird of the far western forests, the Cassin's Vireo is conspicuous for its constant singing. Formerly lumped as a "Solitary Vireo" with the Plumbeous and Blue-headed vireos, it is now considered a separate species.

Description

• Small songbird, medium-sized vireo.
• Brownish-gray head with white spectacles.
• Two whitish wingbars.
• Belly white, flanks yellowish.

• Size: 11-14 cm (4-6 in)
• Wingspan: 24 cm (9 in)
• Weight: 13-18 g (0.46-0.64 ounces)

Sex Differences

Sexes alike, but female slightly duller.

Sound

Song a broken series of slightly burry whistled notes, inflected upwardly and then downwardly. Calls a series of short harsh notes.

Conservation Status

Populations increasing slightly.

Other Names

Viréo de Cassin (French)
Vireo de Cassin (Spanish)
Solitary Vireo (western form) (English)

Cool Facts

• The Cassin's Vireo is the western-most form in the "Solitary Vireo" complex. Formerly considered one species, three species now are recognized. In appearance it is intermediate between the brightly colored Blue-headed Vireo and the dull gray Plumbeous Vireo. Its song also is intermediate between the other two species, being much hoarser than Blue-headed Vireo, but slightly higher and with more clear phrases than Plumbeous Vireo.

• Two subspecies of Cassin's Vireo are recognized. One is widespread in western North America from Canada to the northern part of Baja California. The other form is found only on the very southern tip of Baja California more than 800 km (500 mi) away.

• The Cassin's Vireo is a fearless defender of its nest. Both the male and female will vigorously scold a predator and dive at it. The female often will not leave her nest and sometimes can be picked up off of it by a human observer.

Sources used to construct this page:

Goguen, C. B., and D. R. Curson. 2002. Cassin's Vireo (Vireo cassinii). In The Birds of North America, No. 615 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.