Adult male This plumage is almost entirely bright sky blue, with the deepest blue colouration on the back, wings, rump, and tail and slightly paler blue on the throat, breast, and sides; the undertail coverts and lower belly are primarily whitish. The iris is dark, the short, slender, pointed bill is blackish, and the legs and feet are black.
Adult female Adult females are primarily pale brownish-grey, with a bluish rump and variable blue edges to the primaries, upperwing coverts, and tail feathers; the wing feathers are variably edged with whitish or pale buff. The undertail coverts and lower belly are whitish, and the breast and throat are often washed with buff. Some females are particularly bright, with more extensive and brighter blue on the wings and tail, a bluish tinge on the back, scapulars, and head, and a brighter pinkish-buff wash on the breast. There is a narrow pale whitish eye-ring, and the lores, chin, and malar area tend to be paler grey than the remainder of the head. Bare part colouration is similar to that of the adult male.
Juvenile This plumage is held into the late summer (August), but is lost prior to fall migration. It is similar to the adult female, but the head and upperparts tend to be somewhat browner, the crown is usually finely streaked or spotted with white, the rump is brownish-grey with no bluish tinge, the wings and tail have paler and less extensive bluish colouration, the wing feathers are more prominently edged with buff, and the throat and underparts are browner and coarsely spotted with whitish or pale buff. Bare part colouration is similar to the adults, although young individuals retain a yellow gape at the base of the bill.
Measurements Total Length: 18-18.5 cm Mass: 26.5-32.5 g
Adult males, with their almost entirely sky blue plumage, are very distinctive and are unlikely to be confused with any other species. Male Western Bluebird is darker blue, with chestnut or rufous on the breast, sides, flanks, and scapulars. Adult females, however, do present some significant identification pitfalls, particularly brightly-coloured individuals with brighter and more extensive rufous-buff on the breast. Such individuals can easily be confused with female Western Bluebird, although the Mountain Bluebird can typically be distinguished by its relatively longer tail and longer primary projection which give it a slightly lankier overall shape. Female Western Bluebird also tends to have a brighter rufous-buff wash across the breast and sides (and sometimes extending onto the scapulars) than even the brightest female Mountain Bluebirds. Finally, female Mountain Bluebird typically shows bolder, paler pale feather edges on the wing feathers than female Western Bluebird, which tends to have relatively plainer wings. Juvenile Mountain Bluebird is best distinguished from juvenile Western Bluebird by its relatively less spotted or unspotted upperparts (juvenile Western Bluebird shows bolder and more extensive pale spotting on the back and scapulars).
The song is given primarily during early morning hours and is infrequently heard. It consists of a short series of loud, emphatic phrases and is similar in structure to the song of the American Robin: chow, chow, poly-chow, poly-chow; this song is often given in flight. The male also sometimes gives a soft, repetitious, warbling eeee-ee-e. Calls include a soft, nasal, descending tew or peu and a short, harsh, high-pitched tink or chak. br>Source: Power and Lombardo (1996); Sibley (2000)
Courtship Pair formation occurs on the breeding grounds, with males arriving several days prior to females in order to set up breeding territories and select potential nest sites. Few courtship displays have been documented in this species, and it is unclear what mechanisms aid female mate choice.
Nest This species typically nests in pre-existing cavities in snags, stumps, fenceposts, or nest boxes; nests are rarely placed in holes in earth banks, in old mammal burrows, in the old nests of other bird species (Barn Swallow, Cliff Swallow, American Robin, Dark-eyed Junco), in crevices in abandoned or active buildings, in rock talus, or in cavities in cliffs. Nest height ranges from 30 cm to almost 10 m, although most nests are between 1 and 2 m above the ground. Construction of the actual nest, which consists of a loose cup of grasses, strips of bark, and weed stems at the bottom of the nest cavity, is completed primarily by the female during April or early May. Nest construction generally takes between several days to a week or more.
Eggs A clutch of (4) 5-6 (8) eggs is laid between mid-April (rarely as early as late March) and late May, and is incubated by the female (occasionally the male) for (12) 13-14 (15) days before hatching. Some pairs are double-brooded in B.C., with second clutches occurring between late May and late June (rarely early July); the latest clutches may even represent treble-brooded pairs, or may represent pairs that have lost one or more previous clutches. The smooth, glossy eggs are entirely pale bluish or bluish-white and are paler in colour than the eggs of the Western Bluebird. This species is a rare host for Brown-headed Cowbird parasitism. Eggs are present in B.C. between late March or early April and early August.
Young The young are fully altricial and downy at hatching, with pinkish-grey skin, a yellow-orange mouth, and yellow gape flanges. The nestlings remain inside the nest cavity for 18-23 days, during which time they are tended by both parents. Following fledging, the young remain closely associated with their parents for several weeks before dispersing and becoming completely independent. Nestlings and dependent fledglings are present in B.C. between mid-April and mid-August, with most occurring between late May and late June.
Source: Power and Lombardo (1996); Baicich and Harrison (1997); Campbell et al. (1997)
This species feeds more extensively on invertebrates than most other thrushes, with insects and spiders often comprising more than 90% of the diet throughout the year. It also feeds on small amounts of plant material, such as seeds, fruits, and berries when they are available. A variety of foraging methods are employed, including perch-foraging, ground-foraging, flycatching, and hover-foraging. Foraging birds often perch on elevated, exposed perches in open habitats and fly to the ground to pursue or capture prey items. During hover-foraging, individuals hover momentarily above potential prey items before dropping to the ground for capture.
Source: Power and Lombardo (1996)
This species is characteristic of open habitats wherever it occurs. Migrants and breeding birds are most common in the southern interior in grasslands, sagebrush steppe, clearcuts, burns, open parkland, agricultural areas, ranchlands, open pine forests, subalpine areas, and meadows. The presence of large snags (and their cavities) as well as elevated perches (stumps, fence posts, etc.) are critical components of suitable breeding habitat. On the south coast, most migrants are found in agricultural areas, estuaries, beaches, golf courses, clearcuts, powerline rights-of-way, highway verges, or open hill tops.
Source: Campbell et al. (1997)
Breeds from central Alaska and southern Yukon south through western Canada (B.C. east to southern Manitoba) and much of the western United States (south to California and western Texas, east to western South Dakota and North Dakota). Winters primarily in the western United States and northern Mexico, north regularly to Oregon, Nevada, southern Utah, and Colorado.
Breeding Fairly common to common breeder throughout the south-central and much of the southeastern interior, from the Coast and Cascade Mountains east to the Rocky Mountains and north to the Cariboo-Chilcotin region of the central interior; it is uncommon in the southeastern interior away from the southernmost regions of the Kootenays and the southern Rocky Mountain Trench. Uncommon and local farther north through the central and eastern interior, and rare to locally uncommon in the northern interior (Peace River region, northern Rocky Mountains west to the eastern slopes of the Coast Mountains). Casual extralimital breeder on the southern mainland coast, such as on the Sunshine Coast (Jervis Inlet) and the Lower Mainland. The centre of this species’ distribution in the province is in the arid basins of the south-central interior (Okanagan, Thompson, Nicola, Fraser) as well as in the Chilcotin region of the central interior.
Winter Very rare in winter on southeastern Vancouver Island and the Lower Mainland, as well as in the Okanagan Valley of the south-central interior. Casual elsewhere across the southern interior as well as farther north along the coast to the Queen Charlotte Islands and Skeena River (Terrace). Accidental in winter in the central interior (Chezacut).
Migration Uncommon spring and rare fall migrant on the southern coast, including southern and eastern Vancouver Island, the Sunshine Coast, and the Lower Mainland. Very rare farther north during migration, including the mainland coast, northern and western Vancouver Island, and the Queen Charlotte Islands. Fairly common to common spring and fall migrant in the southern interior, uncommon spring fall migrant in the central interior (except the Cariboo-Chilcotin region, where it is common), and rare to locally uncommon spring and rare fall migrant through much of the northern interior (including the Peace River lowlands); very rare migrant in extreme northeastern parts of the province (northernmost Rocky Mountains, Fort Nelson lowlands, etc.).
This species is a particularly early spring migrant, with the first birds arriving in the Okanagan Valley of the southern interior as early as mid- to late February; peak movements occur through low elevations of the southern interior between mid-March and mid-April. Spring migrants reach the central and northern interior by early to mid-March, with peak northward movements through this region occurring through April. On the southern coast, most spring migrants pass through the Georgia Basin between late March and late April, although some birds occasionally linger into early May.
Fall migration occurs in the interior primarily from August through September, with some individuals beginning to move southward in northern regions of the province as early as late May; most individuals have left northern and central interior by late September (rarely lingering through October), but the species does not depart the southern interior until mid- to late October. On the south coast, the few fall migrants that move through this region occur primarily between mid-September and late October, with individuals occasionally occurring as early as August or lingering into November or even December.
Source: Campbell et al. (1997)
Population and Conservation Status
This species is common and widespread throughout most of the southern interior. Although declines in bluebird populations throughout much of North America were noted during the 20th century, Mountain Bluebird populations in British Columbia and Washington (as well as throughout most of the species’ range) do not appear to have been a part of this decline. Populations have likely increased in may areas in response to the “Bluebird Trail” program that has installed bluebird nest boxes extensively throughout southern and central regions of the province.
Source: Power and Lombardo (1996); Campbell et al. (1997)
This species is monotypic, with no recognized subspecies. It has been recorded hybridizing with both Eastern and Western Bluebirds where their ranges overlap (e.g., hybridizes somewhat regularly with Eastern Bluebird in the northern Great Plains).
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2021. E-Fauna BC:
Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab
for Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
2023-10-02 1:16:31 PM]
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