The Cassin's Vireo was, until recently, considered one species (the "Solitary Vireo), along with the Blue-headed Vireo and the Plumbeous Vireo. The plumage of a Cassin's Vireo is somewhat intermediate between the more boldly colored Blue-headed Vireo, and the drabber Plumbeous Vireo. Each of the three species differ in their primary range and geography can be used to help identify which of the three species is sighted, but the Cassin's and Plumbeous Vireos do have some overlap in range in the West, making differentiation of the two species more difficult.
Habitat
Found in open woodlands in western North America in the summer, most often in oak woodlands in the south or dry conifer forests towards the north. Can be found in a variety of woodland habitats during migration.
Diet
During the summer months, feeds almost exclusively on insects and spiders. In winter, they may augment their diet with some fruits and berries as well.
Behavior
Forages deliberately in the mid- to high-levels of the forest canopy, searching through the foliage and branches for insects. They will also sometimes fly out to capture insects in mid-air.
Nesting
The nest of a Cassin's Vireo is a cup of grasses, weeds, roots, plant down, and other fibers, placed on the branch of a tree, between 5 and 30 feet from the ground. The female lays 3 to 5 eggs, and both parents help to incubate them. Upon hatching, both parents tend to and feed the young.
Song
The song of a Cassin's Vireo is a series of whistled phrases, increasing in pitch and then descending. Also has a harsh call note.
Migration
Birds that summer in the western U.S. and Canada move southward to Mexico for the winter, with some found as far north as southern California and Arizona.
Similar Species
Plumbeous Vireo , Blue-headed Vireo
Conservation Status
Populations of Cassin's Vireos are widespread, common in many parts of its range, and are stable or may even be increasing. The IUCN lists the Cassin's Vireo as a species of "Least Concern" .
Photo Information
Photo taken on May 2nd, 2012 by Bill Bouton , in San Luis Obispo County, California - Photo licensed under Creative Commons Attribution ShareAlike 2.0 Generic License
Interactive eBird Map
Click to access the eBird species page for Cassin's Vireo
