The male Western Bluebird has a brilliant dark purplish-blue throat with rust-colored shoulders and chest, and a lighter-colored gray-blue belly. The female has blue wings with a gray-brown color on the head and back, and a light rust-colored chest. The Western Bluebird may be confused with the Mountain Bluebird, but may be distinguished from it because the Western Bluebird has no rust color on its throat or chest. The Western Bluebird also has a characteristic hunched posture when perched, which the Mountain Bluebird does not. The characteristic call is a short warble, either a soft, short "PEW", which may be extended to a warbling song, or a harsh, chattering "CHUCK". Length is 6½" to 7".
Range: Year-round range is from northern California, across to southern Utah and southwest Colorado, then south into Mexico. Breeding range is from southern British Columbia to northern California. There are also some breeding areas in central Colorado. Winter range is in the desert areas from southern California, Arizona, New Mexico, and western Texas, stretching south into Mexico. The Western Bluebird migrates by day.
Habitat: Though fairly common in Colorado, the Western Bluebird is not as common as the Mountain Bluebird. The Western Bluebird is typically seen in family groups or in small flocks along roadsides or in open forest areas. It is found in Colorado in orchards, farmyards, pastures, forest edges, brushy country, desert areas, along roads, and in open areas with trees. It is often seen on roadside fences and broken branches of pine trees. It is commonly found on both sides of the Continental Divide in Ponderosa pine forests between 5,000 and 8,000 feet. It is also found at higher elevations. Typically seen in Colorado from late-February to early November. In winter, it may stay at night with other individuals in the same nest cavity.
Diet: Like the Mountain Bluebird, the Western Bluebird swoops down from a perch and pursues insects. It also eats caterpillars, grasshoppers, weevils, ants, and moths. It is often found in orchards where it eats fruit. In winter, it also eats berries, such as mistletoe and juniper.
Reproduction: The Western Bluebird lays 4 to 6 eggs that are pale blue (occasionally white) without markings. It typically raises a second brood each year as the first leaves the nest. Both broods depend on the parents for food until grown. The Western Bluebird nests in old woodpecker holes and other tree and fence-post cavities in mountain meadows but, like the Mountain Bluebird, the Western Bluebird has also adapted well to nesting boxes. The courting male may fly in front of the female with his wings spread and then perch next to her. He may also offer food to the female to establish a pair-bond.