“These exquisites, in their quadruple-extract-of-azure garb, are justly ranked the topmost twig of the American ornithological tree.” —William L. Dawson (1: 181)
The Mountain Bluebird is the bluest of the bluebirds, unadulterated by distinct patches of some shade of orange or red. Males of the species are a striking cerulean blue and are especially stunning in the long rays of sunlight early and late in the day.
The attractiveness of this species perhaps belies its considerable hardiness. The Mountain Bluebird breeds at high elevations and latitudes in western North America with a range that extends above timberline in the Rocky Mountains and north into the Yukon and Alaska. Although that distribution alone ensures that many individuals routinely face challenging environmental conditions, the species is also among the earliest-arriving migrants, appearing in late winter when cold, snowy weather persists. Indeed, for early immigrants to the West, and indigenous peoples before them, the return of the Mountain Bluebird was one of the first signs that spring was not far off. Many people in the West still welcome their return each year with delight.
The Mountain Bluebird nests primarily in pre-existing tree cavities, especially old woodpecker holes that, in many places, are probably in limited supply. Intraspecific and interspecific competition for these sites almost certainly has driven the evolution of many aspects of this species’ natural history, including early arrival to the breeding grounds. Across much of its range, the Mountain Bluebird historically has nested largely in patches of burned-over coniferous forest, after woodpeckers have added cavities to the snags and trees left standing. Such habitat is continually created throughout western North America, but in unpredictable locations. The challenges of finding a place to live and nest may have given the species its “wandering genes.” As described in this account, the Mountain Bluebird is a regular vagrant across North America, much to the delight of birdwatchers.
The Mountain Bluebird readily uses human-made nest boxes. This has allowed many members of the general public to enjoy the species, and it has facilitated study by professional ornithologists. This species account contains a wealth of new, unpublished data on many aspects of Mountain Bluebird biology.
Although much is known about this species' biology, there is still a great deal to be learned. A wealth of interesting research awaits.