Vireo cassinii
The Cassin's Vireo (Vireo cassinii) is a small, migratory songbird native to western North America, renowned for its deliberate movements and distinctive song. Measuring approximately 12-14 cm (4.7-5.5 inches) in length with a wingspan of 20-23 cm (7.9-9.1 inches) and weighing 12-18 grams (0.4-0.6 ounces), it sports a dull olive-green back, a gray head, and prominent white 'spectacles' around its eyes. Two distinct white wing bars and a yellowish wash on its flanks are key field marks aiding ...
Found primarily in coniferous and mixed coniferous-deciduous forests, often in montane regions from low to mid-elevations.
Mainly insectivorous, consuming caterpillars, beetles, true bugs, and spiders; supplements its diet with small fruits and berries, especially during migration and winter.
Cassin's Vireos are diurnal, active foragers, spending their days methodically gleaning insects from the foliage of trees and shrubs, often moving slowly and deliberately. Males are highly territorial during the breeding season, defending their home range with persistent singing from prominent pe...
The breeding range of the Cassin's Vireo extends across western North America, from southern British Columbia through the mountainous regions of Washington, Oregon, and California, eastward into Idaho, western Montana, Nevada, Utah, and western Colorado. Isolated breeding populations also occur i...
Least Concern
- The Cassin's Vireo was once grouped with the Blue-headed and Plumbeous Vireos, collectively known as 'Solitary Vireos,' before genetic and vocal analyses led to their species-level separation. - Its distinct, deliberate, and often questioning song (e.g., 'chew-wee? chew-whit!') is a primary way...