Mountain Bluebird

About

The Mountain Bluebird is a medium-sized thrush known for its striking sky-blue plumage in males and more subdued blue-gray tones in females. It is an iconic species of western North America's open, high-elevation habitats, often seen hovering while foraging for insects.

Size & lifespan

Length

15.5-18 cm (6.1-7.1 in)

Wingspan

33-35.5 cm (13-14 in)

Weight

28-32 g (1.0-1.1 oz)

Lifespan

Typically 6-10 years in the wild, with records up to 12 years.

Diet

Omnivore, primarily insectivorous during breeding season, supplementing with berries and fruits in winter.

Physical characteristics

Plumage

Adult males are almost entirely brilliant sky-blue, often appearing iridescent. Adult females are duller, with a gray-brown body, pale blue on the wings and tail, and sometimes a faint blue wash on the rump. Juveniles are gray-brown with heavy spotting on the breast and back, and blue only on the wings and tail, gradually acquiring adult plumage.

Beak shape

Slender, pointed, and relatively short; black in color.

Eye color

Dark brown

Leg color

Black

Distinguishing features

Males are unmistakable with their uniform, vibrant blue plumage. Females are distinguished from other bluebirds by the lack of rufous on the breast or flanks, and a generally paler, more grayish appearance with blue restricted to wings and tail. Their habit of hovering while foraging is also a key field mark.

Juvenile appearance

Gray-brown overall with distinct white spotting on the breast and back, resembling a young thrush. Blue is restricted to the primary feathers and tail. They gradually molt into adult plumage.

Seasonal changes

Plumage does not change significantly between breeding and non-breeding seasons, though fresh plumage may appear slightly brighter due to less feather wear.

Sexual dimorphism

Pronounced. Males are brilliant sky-blue all over, while females are much duller, primarily gray-brown with limited blue on wings and tail.

How to identify

1. 1

   Overall Color (Males)

   Look for a bird that is entirely brilliant sky-blue, with no rufous or white on the underparts. This is the most distinctive feature.

2. 2

   Overall Color (Females)

   Observe for a bird that is predominantly gray-brown, with pale blue restricted to the wings and tail, and sometimes a faint blue wash on the rump. Absence of rufous on the breast/flanks is key.

3. 3

   Foraging Behavior

   Watch for their characteristic hovering flight over open ground, where they hang in the air before dropping to catch insects. This behavior is less common in other bluebird species.

4. 4

   Habitat

   Consider the location. Mountain Bluebirds prefer open, high-elevation habitats in western North America, often in meadows or sagebrush flats, whereas Western and Eastern Bluebirds prefer more wooded or suburban areas.

5. 5

   Song/Calls

   Listen for their soft, warbling, high-pitched song or their distinctive 'few' or 'chur' calls, which are generally softer than other bluebirds.

Habitat & range

Biomes

Temperate grasslands, shrublands, open woodlands, subalpine meadows, and agricultural areas.

Geographic range

Western North America, from Alaska and western Canada south through the western United States to central Mexico. Breeding range extends from central Alaska, Yukon, and western Northwest Territories south through British Columbia, Alberta, Saskatchewan, and Manitoba, and throughout the western US states. Winters primarily in the southwestern US and Mexico.

Elevation range

Breeds at higher elevations, typically 1,500-3,500 meters (5,000-11,500 feet), but can be found lower during migration and winter, down to sea level in some areas.

Preferred environments

Open country with scattered trees or shrubs, often near clearings, pastures, sagebrush flats, and high-elevation meadows. They prefer areas with available nest cavities, such as old woodpecker holes or nest boxes.

Behavior

Activity time

Diurnal.

Feeding habits

Primarily insectivorous, especially during the breeding season. They forage by perching on a low branch or fence post, scanning the ground, then dropping to catch insects. They are also well-known for their hovering flight, where they hang in the air to spot prey before swooping down. Diet includes grasshoppers, crickets, beetles, caterpillars, and flies. In fall and winter, they supplement their diet with berries and small fruits.

Social behavior

Typically solitary or in pairs during the breeding season. Outside of breeding, they may form small flocks, sometimes mixed with Western or Eastern Bluebirds, especially during migration and winter.

Flight pattern

Often flies with a buoyant, undulating motion. Distinctive hovering flight while foraging is a key characteristic.

Migration pattern

Migratory, though some populations in the southern parts of their range may be resident or undertake short-distance altitudinal migrations. Northern populations migrate south to the southwestern US and Mexico for winter. Migration occurs in loose flocks.

Territoriality

Males establish and defend breeding territories, primarily around the nest site. They will aggressively defend against other bluebirds and cavity-nesting competitors.

Breeding & reproduction

Breeding season

Typically April to August, with peak activity in May and June. May raise one or two broods per season.

Nesting habits

Cavity nesters, utilizing old woodpecker holes, natural tree cavities, rock crevices, and readily using nest boxes. The female builds the nest, which is a loose cup of grass, weeds, and sometimes hair or feathers, placed inside the cavity.

Clutch size

4-7 eggs

Egg description

3-8 (typically 4-7) pale blue, unmarked eggs. Occasionally, eggs may be white.

Incubation period

13-14 days, primarily by the female.

Fledging period

20-23 days after hatching. Young leave the nest but are still fed by parents for a period.

Parental care

Both parents feed the nestlings and fledglings. The male may continue to feed the first brood while the female starts a second clutch.

Where to find

Field tips

1. Scan open areas. Mountain Bluebirds prefer wide-open spaces. Look for them perched on fence posts, power lines, or low branches, scanning the ground for insects.
2. Watch for hovering. Their unique hovering flight while foraging is a strong identification clue. They will often hover for several seconds before dropping to the ground.
3. Visit at appropriate elevations. During the breeding season, focus your search on higher elevations in mountainous regions. In winter, they may descend to lower valleys.
4. Look for nest boxes. If you are in suitable habitat, check any installed nest boxes, as they are a favored nesting site.

Similar species

Quick facts

Primary Habitat:

Open, high-elevation western North America

Distinctive Male Feature:

Entirely sky-blue plumage

Foraging Style:

Hovering flight

Nest Type:

Cavity nester (natural cavities, nest boxes)

Diet Focus:

Insects (summer), berries (winter)

Fun facts

• The Mountain Bluebird is the state bird of Idaho and Nevada.
• Unlike many other bluebirds, the male Mountain Bluebird lacks any rufous (reddish-brown) plumage, making him entirely blue.
• They are highly adaptable to using human-provided nest boxes, which has helped their populations in some areas.
• Their hovering flight is a specialized foraging technique that allows them to spot ground insects from above, similar to kestrels.
• During severe winter weather, Mountain Bluebirds have been observed huddling together in cavities for warmth.

Scientific classification

Kingdom

Animalia

Phylum

Chordata

Class

Aves

Order

Passeriformes

Family

Turdidae

Genus

Sialia

Species

Sialia currucoides

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