• Adult on nest.

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Cassin's Vireo

Vireo cassinii
Members of this diverse group make up more than half of the bird species worldwide. Most are small. However their brains are relatively large and their learning abilities are greater than those of most other birds. Passerine birds are divided into two suborders, the suboscines and the oscines. Oscines are capable of more complex song, and are considered the true songbirds. In Washington, the tyrant flycatchers are the only suboscines; the remaining 27 families are oscines.
This family is found only in the New World. Vireos are small birds that move about slowly and deliberately as they glean insects from foliage and twigs. Their bills are cylindrical, with a slight hook at the end. These bills are relatively large for birds their size, which enables them to eat fairly large insects. Most vireos are drab colored, with olive-green or yellow upperparts and lighter olive or buffy underparts. Many have eye-rings, eye-lines, or wing-bars. In Washington, vireos with wing-bars have eye-rings, and those without wing-bars have eye-lines. Vireos are often hard to see as they forage in high or thick foliage, and when found are generally alone or in pairs rather than in large flocks. Most have fairly simple songs that they sing repeatedly, many singing through the entire day and even while on the nest. Nests are generally suspended from small horizontally forked branches. Pairs are monogamous, and both parents raise the young.
Fairly common summer resident.
  • Species of Concern

General Description

Formerly known as the Solitary Vireo, the Cassin's Vireo is now one of three separate species. Cassin's Vireos are olive above and whitish below, with a yellowish wash on their sides and flanks, white throats, and gray heads. They have two white wing-bars and distinctive white eye-rings that extend to the brow, making the birds look as if they are wearing spectacles.


The Cassin's Vireo is the only Washington vireo characteristically found in conifer forests. While these birds appear to prefer dry conifer forests of Douglas fir and Ponderosa pine, they can also be found in mixed coniferous and broadleaved forests, and may prefer to nest in hardwood trees.


Cassin's Vireos are inconspicuous as they work their way along branches, twigs, and leaves, looking for food high up in the trees. Occasionally they fly out to grab flying insects in midair, but most of the time they glean from various surfaces. During spring and early summer, they sing incessantly, revealing their presence.


Insects are the primary diet, although Cassin's Vireos will sometimes eat berries and other small fruits, especially in winter.


Cassin's Vireos build a bulky nest suspended in a low horizontal fork of a tree branch. Both members of the pair help build the nest, which is made of grass, bark strips, rootlets, and other plant fibers, lined with hair and plant down, and adorned on the outside with moss and pine needles. Both parents incubate the three to five eggs for 12 to 14 days, and both feed the young, which leave the nest at about two weeks of age.

Migration Status

Some of these Neotropical migrants winter as far north as the southwestern United States, but most winter in Mexico. They arrive on the breeding grounds a bit earlier in spring, and stay a bit later in the fall than other vireos.

Conservation Status

In some areas, Cassin's Vireos are heavily parasitized by Brown-headed Cowbirds. They are listed on the Audubon~Washington Watch List as a species-of-concern in the state, although, according to the Breeding Bird Survey, the population in Washington increased significantly between 1980 and 2000.

When and Where to Find in Washington

Cassin's Vireos are fairly common and widespread in eastern Washington in lower- and moderate-elevation conifer forests in the eastern Cascades, the northeastern corner, and the Blue Mountains. Although generally uncommon in western Washington, they are locally common along major river valleys and dry forests in the Puget Trough, such as the San Juan Islands, the northeastern Olympic Peninsula, Fort Lewis (Pierce County), and Ross Lake (Whatcom County).

Abundance Code DefinitionsAbundance

C=Common; F=Fairly Common; U=Uncommon; R=Rare; I=Irregular
Pacific Northwest Coast UUUUUU
Puget Trough RFFFFU
North Cascades RUUUUR
West Cascades RUUUUU
East Cascades UFFFFU
Okanogan UCCCCU
Canadian Rockies UUUUU
Blue Mountains FFFFU
Columbia Plateau UUUUUU

Washington Range Map

North American Range Map

North America map legend

Federal Endangered Species ListAudubon/American Bird Conservancy Watch ListState Endangered Species ListAudubon Washington Vulnerable Birds List
Early Warning

View full list of Washington State's Species of Special Concern