The Western Bluebird

(Sialia mexicana)

by Jay Sharp

Western Bluebird

For a creature so small — it’s smaller than an American robin — the bluebird, in its bejeweled brilliance, has become an outsized symbol of joy and happiness in American culture. Composer Richard A. Whiting wrote songs about the bluebird. Judy Garland sang about the bluebird in her classic movie The Wizard of Oz. Shirley Temple sang about it in her movie named The Blue Bird. Duke Ellington and Billy Strayhorn performed songs about the bluebird. Dinah Washington sang about the bird in “Blue Skies:”

“Bluebirds singing a song,
“Nothing but bluebirds from now on.”

Even before European peoples arrived in America, the Navajos embodied the bluebird in their rituals and folk beliefs, believing it signaled sunrise and renewal.

Distinctive Features

The western bluebird, like its cousins the eastern bluebird (Sialia sialis) and the mountain bluebird (Sialia currucoides), belongs to the Thrushes, a large family of perching birds that typically feed on insects and fruits.

  • Size: Length, about 7 inches; wingspan, about 13.5 inches; weight, about an ounce, said David Allen Sibley in his The Sibley Guide to Birds.
  • Adult male plumage: Bright cobalt-blue head, throat, back and wings; chestnut breast, shoulders and under-wing feathers; light blue to bluish gray to gray belly and under-tail feathers.
    (The eastern bluebird, while similar, has more chestnut color on its throat and neck and has a lighter-colored belly and under-tail feathers. The mountain bluebird, according to authorities Judith A. Guinan, Patricia A. Gowaty, and Elsie K. Eltzroth, has a longer and thinner shape, a lighter color blue and minimal chestnut colors.)
  • Adult female plumage: Faded blue head, throat, back and wings; dull chestnut breast, shoulders and under-wing feathers; dull gray belly and under-tail feathers.
  • Voice and sounds: A short, sometimes warbled “pew” or a chattered “chuck,” according to the Colorado Division of Wildlife.

Distribution and Migration Habits

The western bluebird occurs from the southwestern corner of Canada southward through the Pacific Coastal regions of the United States into the upper Baja peninsula of Mexico, and it covers much of the Southwest Four Corners region southward into central Mexico, say Guinan, Gowaty and Eltzroth.

Some western bluebird populations migrate with the seasons and the weather. Other populations remain in the same location through the year. Those that do migrate follow a mixed agenda, often moving in scattered flocks and flying at considerable heights. Some populations move south and north with the seasons, sometimes temporarily joining year-round populations. Other populations merely alternate between higher and lower elevations, responding to the seasons and local weather conditions. Populations move at different times in different locations, following routes that have never been fully resolved by ornithologists.

Habitat and Diet

During the breeding season, the western bluebird populations in the Southwest tend to seek out wooded mountain flanks and river bottoms as well as some pasture and farmlands for nesting sites. For instance, in south-central Colorado, southern Utah, northern Arizona, and northern New Mexico, the bird sets up housekeeping in the piñon pine-juniper woodlands of the lower elevations up to the ponderosa pine forests of the higher elevations, usually preferring the more open park-like areas.

During the colder seasons, the Southwest breeding populations often move to lower elevations, making a winter home near the desert wetlands, the riverine woodlands, mesquite growths and the lower mountain woodlands.

In the breeding ranges, during the nesting season, the bird seems to prefer preying on arthropods, feeding, for instance, on grasshoppers, crickets, caterpillars, beetles, ants, wasps, bees and spiders. It may beat larger prey against a hard surface to kill it before eating it. In winter ranges, it turns more to fruits, including, for example, juniper berries, mistletoe berries and grapes. Rarely, a western bluebird may prey on small reptiles.

Behavior and Life Cycle

Western bluebird males and females form long-term, though not always faithful, bonds. During courtship between a bonded pair, say Guinan, Gowaty and Eltzroth, the male hovers or perches before the nest entrance, fluttering its wings and offering food and nesting material before the female. A particularly receptive female may flutter her wings, crouch her body and raise her tail to signal her sexual readiness. After mating, the male tends the expectant mother carefully, guarding her and feeding her while she lays and incubates the eggs.

Outside the bond, in what ornithologists call “extra-pair copulation,” the male tries to woo a female by shivering all over, waving its wings and tilting its body amorously. If she is interested, she may respond by snapping, pecking and grappling flirtatiously. If she is not interested, she may simply fly away.

Typically, a bonded pair searches jointly for a nesting site, seeking out cavities in live or, perhaps more often, dead oaks, willows, pines or other tree species. (Occasionally, the western bluebird may build a nest in the abandoned mud nest of a Cliff Swallow or in protected nooks in rural houses or barns.) Although she may be accompanied by the male, the female carries the main burden of building the nest. She gathers materials such as twigs, grass, pine needles, mosses and even mammal fur or horse hair to build a neat, loosely woven, lined, cup-shaped nest about five inches in diameter within a chosen cavity.

A few days after she completes the nest, the female begins laying her clutch of four to six three-quarter-inch long light blue to white eggs at a rate of one a day, according to Gregory Gough, with the U. S. Geological Survey. Fed by the male, she broods her clutch for about two weeks, when her pinkish, faintly peeping chicks emerge from their shells.

The parents provide a steady diet of insects to their young charges, which fledge within about three weeks and become independent within next several weeks. If conditions are right, the parents may then produce a second brood. With luck, a western bluebird may live for several years.

Life’s Hazards

The western bluebird’s eggs and nestlings sometimes suffer predation by a small mammal, for instance, a chipmunk, squirrel or weasel, or occasionally by a snake, for example, a kingsnake or a gopher snake. Nestlings may also fall prey to domestic cats.

Fledgling as well as adult western bluebirds are taken by predatory birds. Parents may attempt to defend their nest by flying directly at the predator, with chattering and bill snapping, hoping to put the adversary to flight. In some areas, said the Seattle Audubon Society, western bluebird populations are declining as a result of competition from invasive bird species, loss of habitat and regional changes in climate.

Interesting Facts

  • Parent western bluebirds often beat larger prey repeatedly against a hard surface — presumably to make it easier to consume — before offering it to nestlings, according to Guinan, Gowaty and Eltzroth.
  • Sometimes, the parents received help from unrelated western bluebird adults and even other species’ adults (for instance, violet-green swallows) in feeding hatchlings and defending the nest.
  • A high percentage of western bluebird hatchlings, studies have shown, have been fathered by a male other than the bond male.

Mister Bluebird on my shoulder
It's the truth, it's actch'll
Ev'rything is satisfactch'll
Zip-a-dee-doo-dah, zip-a-dee-ay
Wonderful feeling, wonderful day!

(From the Walt Disney classic: Song of the South)

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