Brian E. Small
Chiefly a resident of the open country of the western United States, the Mountain Bluebird (Sialia currucoides) stands out as perhaps the most beautiful of the three bluebird species. The Mountain Bluebirds' close cousins, the Eastern and Western Bluebirds, are a striking combination of blue, rusty brown and white, but there is nothing quite like the subtle yet spectacular sky-blue plumage of an adult male Mountain Bluebird.
Despite their similar coloring, the Mountain Bluebird may differ from its cousins in average length, ranging from 6.5 inches to 7.25 inches. It also possesses a longer, thinner bill and longer wings, tail and legs.
The Mountain Bluebird's breeding range extends from parts of Alaska all the way south and east into New Mexico. Mountain Bluebirds can be found in a variety of habitats west of the Mississippi and are found in open areas with some trees during the nesting season and in a variety of treeless terrain during the winter months. They can be heard by their thin few or chur call and low, warbling tru-lee song.
Interestingly, studies have shown that birds reared in a nest box will imprint to it and seek that type of box for future nesting attempts. Mountain Bluebirds compete with Northern Flickers, House Wrens, House Sparrows, starlings and swallows for nest sites, but because they nest in more remote areas, they are less affected than the other bluebirds by this competition.
As food supplies decrease at both higher elevations and northern latitudes during fall, Mountain Bluebirds migrate downslope and south in search of a reliable food source. They winter from the coast of California eastward into New Mexico and Texas, and stray birds occasionally appear on the Atlantic Coast.
In the wintertime, birders should search sagebrush flats, pinyon-juniper woodlands, open grasslands, deserts, farmlands and plowed fields for this lovely member of the thrush family. Also during winter, Mountain Bluebirds often gather into flocks of as many as 100 birds or more.
Unusual feeding behaviors make Mountain Bluebirds fairly conspicuous. Keep a sharp eye out for them hovering low over an open field and then dropping quickly to the ground for insects. They like to hover more than the other bluebirds and also can be seen perched low to the ground, poised to catch flying insects.
Their delicate pastel coloring, interesting feeding behavior, relative tolerance of humans and ability to use nest boxes are just some of the characteristics that attract birders to the Mountain Bluebird. Watch for them on your next trip out west, and you, too, may get hooked on the bluebird of happiness.
Mating: Little is known about the mating habits or displays of Mountain Bluebirds.
Nest Sites: Most often selected by the female. Mountain Bluebirds use natural tree cavities, old woodpecker holes, old Cliff Swallow nests, and nest boxes. Most often found above 7,000 feet in subalpine meadows, open deciduous and coniferous forests and other open country.
Nest: Built by both the adults within the cavity. Consists of a loose cup of twigs, weed stems, shreds of bark, grasses, pine needles and rootlets. Often lined with animal hair or feathers.
Clutch: Four to eight bluish-white or pale blue unmarked eggs. Mountain Bluebirds often produce two broods in a season.
Incubation Period: The female incubates the eggs for 13 to 17 days, and the male will feed her during this time.
Nestling Period: The nestlings are altricial and will be fed by both of the adults for about three weeks.
Fledging Period: The young will leave the nest about three weeks after hatching and will be tended by the parents for another three to four weeks after leaving the nest cavity.
Food: Primarily, the adults feed themselves and the growing chicks insects, including grasshoppers, caterpillars, crickets, ants, bees, beetles and more. Known to hover above prey before catching them. During winter, they are more dependent on the berries from mistletoe, juniper and hackberry plants.
National Club: North American Bluebird Society (Website here.)