Western Bluebird

The western counterpart of the more familiar eastern species, the western bluebird actually has more extensive blue and overall richer coloration than its popular cousin. Though these birds do not use bird houses as regularly, they are still welcome guests in western backyards.

Common Name:

Western Bluebird

Scientific Name:

Sialia mexicana

Scientific Family:

Turdidae

• Bill: Black, straight
• Size: 7-7.5 inches long with 12-13-inch wingspan, stocky build, large head
• Colors: Blue, chestnut, gray, buff, white, brown-gray
• Markings: Dimorphic species. Males have a rich blue hood and bright blue wings and tail. The amount of chestnut on the back can vary and may be covered with a dark blue or gray wash. The breast and flanks are chestnut, while the lower abdomen and undertail coverts are gray-white. Females have a gray throat, pale blue head and nape and a prominent white eye ring. The back is brown-gray, and the wings, tail and rump are a bright blue, though not always as bright as a male's coloration. The breast, sides and flanks are chestnut, and the belly and undertail coverts are gray-white. Eyes are dark and legs and feet are black for both genders. Juveniles are brown-gray with heavy white or buff spotting, showing a blue wash on the wings and tail.

Insects, spiders, snails, worms, berries (See: Insectivorous)

Habitat and Migration:

These thrushes prefer open woodlands, either coniferous or deciduous, as well as riparian habitats, scrubby deserts and agricultural areas. They can also be found in suburban parks and golf courses, though they are rarely found in heavily urbanized regions.

The western bluebird's year-round range includes southern Utah, Arizona, New Mexico and coastal and central California north to central Oregon, and south to central Mexico. In summer, their breeding range extends as far as Idaho, Washington, Colorado, western Nevada and into British Columbia. In winter, northern breeding birds will migrate, and the winter range includes more extensive habitats to the southeast of the year-round range, including western Texas and a wider range in Mexico.

These birds have a sharp, fast "kew-kew" song that can be repeated rapidly for a longer string of syllables. It may have a raspy quality, and the pitch and rhythm can vary. A chatter call is also commonly heard.

These birds stay in pairs or small family groups for most of the year, but can be found in larger mixed flocks in winter with American robins, mountain bluebirds, yellow-rumped warblers and other species with similar foraging habits. They forage on the ground, often dropping from an elevated perch and returning to that perch to feed. Western bluebirds will also catch insects in flight. On the coldest winter nights, these birds have been observed using communal roosting cavities, such as bird roost boxes, with multiple adults sharing the same space for heat conservation.

These are monogamous birds that mate after brief courtship displays that include exaggerated flights and males offering potential females food. Both mates then construct a nest in an appropriate cavity 2-50 feet above the ground. The nest is relatively loose and may include grass, weeds, twigs and pine needles.

There are 2-8 eggs per brood, and 1-2 broods are typical for each mating season. The oval-shaped eggs are pale blue-white. The female parent incubates the eggs for 13-14 days, and both parents feed the altricial young for an additional 14-22 days after hatching. Unmated males in the area may serve as "nest helpers" and help feed the chicks as well.

Western bluebirds occasionally hybridize with mountain bluebirds.

Leaving dead trees with woodpecker holes or natural cavities intact as nesting sites can help attract these birds. At backyard feeders, western bluebirds will readily take suet, mealworms, peanut butter and raisins, and berry bushes such as sumac, blackberries, juniper and elderberries are ideal natural food sources to leave available for overwintering birds. Wood or wire fences provide preferred perches for foraging bluebirds, and they will readily visit bird baths.

While these thrushes are not endangered, habitat loss, particularly in nesting areas, can be a significant threat. These birds require old trees that include abandoned woodpecker holes to serve as nesting sites, and removal of these trees for development or aesthetic reasons decreases their nesting success and can impact populations. European starlings and house sparrows also compete with western bluebirds for nesting sites and may even kill eggs, chicks or brooding adults. Adding nesting boxes in western bluebird habitats can be helpful, though this species does not use bird houses as readily as its eastern counterpart.

• Eastern Bluebird (Sialia sialis)
• Mountain Bluebird (Sialia currocoides)
• Lazuli Bunting (Passerina amoena)
• Red-Flanked Bluetail (Tarsiger cyanurus)

Photo – Western Bluebird – Male © Michael Woodruff
Photo – Western Bluebird – Female © Michael Woodruff