Mountain Bluebird

The Mountain Bluebird is a thrush of western North America. It is striking and charismatic and is one of the most beautiful birds of the west. Its range is from Alaska, noncoastal BC, Alberta, to central Manitoba, south to western Oklahoma extending west to the mountains of southern California. It winters in the southern parts of its breeding area and in Mexico.

Adult Male (spring/summer)

Cerulean to turquois blue above with paler lighter blue breast, white belly and vent. Wing tips are dusky. Legs are black. The beak is thin and black. Irises are black with a very pale eye ring.

Adult Female (spring/summer)

Plain ashy-gray overall with a touch of pale cerulean blue on the rump, tail, and flight feathers; white eye ring; white vent; and sometimes a faint malar streak.

Juvenile

Like adult female but darker and duller; breast and sides streaked with grayish brown, the center of each feather with a white spot.

General:

The largest and most sleek bluebird. Length: 16.5-20cm. Wing: 35cm. Weight: 29 grams.

Behaviour:

The Mountain Bluebird hovers low over the ground and drops down to catch insects or darts out from a tree branch, rock or other elevated position in a flycatcher fashion. It feeds heavily on insects and also eats some berries, which are particularly important during winter.

Habitat:

Open areas where mountain meadows and pastures are interspersed with loose stands or single coniferous trees. Open rangeland, sagebrush and lowland prairies as well as alpine zones above the treeline. Often found in flocks during winter.

Information:

The Mountain Bluebird lives in more open terrain than the two other bluebirds. It may nest in holes in cliffs or dirt banks when tree hollows are not available. It is an opportunistic species that reap huge increases in its populations when people clear forests, raise grazing livestock and erect nest boxes. They readily accept nest boxes, which also make this species vulnerable to human-associated hazards such as pets, vandals, and dense rodent populations. Most of what is known about this species is based on studies of nest box populations, not natural ones. Pairs produce 4-6 pale greenish-blue eggs.

Similar species:

Western Bluebird, Eastern Bluebird.

Conservation Status:

Populations appear to be stable throughout the breeding range. Listed as Least Concern.

Capture Rates:

Although appropriate habitat at Colony Farm, Mountain Bluebird breeding range doesn’t extend to coastal areas of British Columbia. These bluebirds are seen passing through on their way north and west as reflected by the capture rates of a few individuals in April.

Molt Summary:

PF: HY partial (Jul-Sep): PB: AHY complete (Jul-Sep); PA absent.
PBs occur on the summer grounds.
Preformative molt includes 1-8 inner gr covs and rarely 1-2 central rects, but no terts.

This SY male in April is showing a clear molt limit between the 5 replaced inner greater coverts and 5 retained outer greater coverts (red arrow). Notice the contrast between the worn and brownish retained feathers and fresher brighter blue feathers. Notice also the relatively tapered outer primary coverts tinged brownish and dull brownish alula.

This SY male in April is also showing a clear molt limit between the 5 replaced inner greater coverts and 5 retained outer greater coverts (red arrow). Notice again the contrast between the worn and brownish retained feathers and fresher brighter blue feathers. Notice also the very tapered and much more brownish outer primary coverts and very dull, almost entirely brownish alula.

This SY female in April is also showing a molt limit within the greater coverts but as females have dull brownish to grayish body plumage unlike the more bluish body plumage of males the molt limit is less obvious. Notice the worn and pale brownish 7 retained outer greater coverts contrasting with the bluish gray 3 replaced inner greater coverts (red arrow). Notice again the relatively tapered outer primary coverts tinged brownish and dull brownish alula.

The super-macro shot of the greater coverts of the above SY female in April shows the contrast between retained and replaced feathers in close-up (red arrow).