This tiny, thin-billed, wing-flicking insectivore is grayish olive with a conspicuous broken white eye ring. Polytypic. Length 4.2".
Adult male: bright greenish gray above, paler below; broad, teardrop-shaped white eye ring, slightly broken at the top (especially) and bottom; lores olive. Ruby crown patch visible only during display, or when bird is agitated. Black at base of secondaries, contrasting with white lower wing bar. Adult female: similar to male, no ruby crown patch. Immature: somewhat pointier tail feathers than adult, a few males may have orange, yellow, or olive crown patch.
Northwestern subspecies (grinnelli) slightly darker.
Compare with Hutton’s vireo.
Call: most frequently heard is a husky 2-syllable ji-dit. Song: often heard in migration; begins with 2–3 very high-pitched notes, abruptly changing to a rich, and surprisingly loud warble: tsii tsii tsii chew chew chew teedleet teedleet teedleet.
Status and Distribution
Common. Breeding: breeds in boreal spruce-fir forests, preferably near water and especially in black spruce bogs. Breeding begins immediately when females arrive in early May. Nest: high in conifer near trunk, 8–12 eggs (May–June) is largest clutch size of any passerine in North America. Spring migration: as late as early May in Mexico. March to early May, in southern United States. Early April to late May, peaking late April to early May in central and northeastern United States. Fall migration: begins mid-September; peaks late September to mid-October; continuing through mid-November Arrives as early as late Sept. in Florida and Mexico. Winter: not as hardy as the golden-crowned, and winters farther south in a broad range of habitats. Primarily southern and western. United States through Mexico to Guatemala. Vagrant: Yucatán Peninsula of Mexico, Bahamas, western Cuba, Jamaica (sight rec.), Greenland (2 recs.) and Iceland. Many records from ships off Atlantic coast, but no confirmed records from western Europe.
Breeding areas in the western United States may be adversely affected by logging and wildfire.
—From the National Geographic book Complete Birds of North America, 2006