Bird of the Month: Western Bluebird
Written by Andy McCormick
Andy McCormick, Volunteer and Former Board President of Eastside Audubon
A bird of open woodland, the Western Bluebird brings a special beauty to the Washington landscape.
The Western Bluebird is a small, quiet thrush. The male is a striking cobalt blue on the head, chin, throat, wings, and tail, and rust coloration on the chest and part of the scapulars. The female is a smooth gray on the head and back with pale orange on the breast. This bluebird is a bird of open woodland in contrast to the Mountain Bluebird (S. currucoides) which prefers open fields. The Western is a short-distance migrant never straying far from its breeding area, but it does completely abandon the breeding area in Washington by October. Most arrive in eastern Washington by April, but some appear in late February. They begin nesting shortly after a pair bond is formed. You can view photos and video of these beautiful birds at the Macaulay LIbrary.
CAVITY NESTER
The Western Bluebird is a secondary cavity-nesting species, and it forages from a perch. These attributes make it reliant on older, decaying trees and snags, and large trees with previously constructed cavity nests. They require an environment of open forest with a mix of a few trees and open areas into which the bluebirds can forage (Guinan, et al). They usually fly down to the ground to take insects.
The male and female search for a suitable nesting site together, but most observers report that the female alone builds the nest of twigs and weeds within the tree cavity. Usually, 4-6 pale blue eggs are deposited. Incubation is completed by the female in about two weeks and the young fledge about three weeks after that (Guinan, et al). Both parents bring food to the nestlings.
Western Bluebird
Scientific Name: Sialia mexicana
Length: 7”
Wingspan: 13.5”
Weight: 1 oz (29g)
AOU Alpha Code: WEBL
FIRST NAMED IN MEXICO
The Western Bluebird has a breeding range that includes a large portion of northern Mexico. Its species epithet, mexicana, refers to the location for which the bird was named by William Swainson (1789-1855), who was friendly with William Bullock (1773-1849), who owned a silver mine in Mexico, and his son, also William Bullock, who was an avid collector of birds in Mexico. Once the Bullocks returned to England, Swainson, reviewed all of Bullock’s birds specimens and organized the bird taxonomy and naming (Mearns and Mearns). This is a good example of the manner in which early European-Americans named North American birds. The Western Bluebird shares the genus Sialia, from the Greek, sialis, a kind of bird, with the Eastern and Mountain Bluebirds.
STATUS AND DISTRIBUTION
The Western Bluebird has a breeding range that extends from southern British Columbia through the woodland areas in western Montana and Idaho, and the eastern portions of Washington, Oregon, and a year-round range west of the Rocky Mountains in California and the southwest, and south into Mexico. The population of Western Bluebirds has declined significantly in Washington since the 1950s. These birds were once common west of the Cascades, but due to human development, conversion of oak and prairie habitats, removal of snags, and fire suppression reducing the amount of burned area, Western Bluebirds now nest east of the Cascades and in a small area known as the South Sound prairies west of the Cascades.
Fortunately, the Western Bluebird takes readily to bird houses, and to compensate for the removal of snags and older trees, many organizations have supported the placement of “nest-box trails” in areas once frequented by bluebirds. Outcomes have been positive. A nest-box trail in the Spokane area produced an average of 173 fledglings between 1976 and 1981. A similar program at Fort Lewis in Pierce County increased breeding pair numbers to 215 in 1988, with 700+ fledglings produced in 1989. However, long term recovery of the Western Bluebird will require improvements in the natural habitat using controlled burns to maintain an open forest canopy, preservation of snags in clear cuts, and in the interim period, continued expansion of nest-box trails (Wahl, et al.)
Photo credit by ______. References available upon request from amccormick@eastsideaudubon.org.