The mountain bluebird (Sialia currucoides) is a migratory small thrush that is found in mountainous districts of western North America. It has a light underbelly and black eyes. Adult males have thin bills and are bright turquoise-blue and somewhat lighter underneath. Adult females have duller blue wings and tail, grey breast, grey crown, throat and back. In fresh fall plumage, the female's throat and breast are tinged with red-orange which is brownish near the flank, contrasting with white tail underparts. Their call is a thin 'few' while their song is a warbled high 'chur chur'. The mountain bluebird is the state bird of Idaho and Nevada. This bird is an omnivore and it can live 6 to 10 years in the wild. It eats spiders, grasshoppers, flies and other insects, and small fruits. The mountain bluebird is a relative of the eastern and western bluebirds.
Taxonomy
The mountain bluebird was formally described in 1798 by the German ornithologist Johann Matthäus Bechstein and given the name Motacilla s. Sylvia currucoides. The specific epithet combines curruca, from Carl Linnaeus's binomial name Motacilla curruca for the lesser whitethroat with the Ancient Greek -oidēs meaning "resembling". The mountain bluebird is now placed with the two other bluebirds in the genus Sialia that was introduced by the English naturalist William John Swainson in 1827. The species is monotypic: no subspecies are recognised.
Description
The mountain bluebird is in length, weighs , and has a wingspan of 11.0-14.2 in (28-36 cm). It is sexually dimorphic in the color of the plumage but the sexes are similar in size. An adult male is bright turquoise-blue above and somewhat lighter blue underneath but with a white lower belly. An adult female has duller blue wings and tail, grey breast, grey crown, throat and back. In fresh fall plumage, the female's throat and breast are brownish near the flank, contrasting with white tail underparts. Their call is a thin 'few'; while their song is warbled high 'chur chur'.
Distribution and habitat
Their breeding habitat is open country across western North America, including mountainous areas, as far north as Alaska. Although mountain bluebirds can be found in some states year-round, their range is expansive — they generally migrate south to Mexico in the winter and north into western Canada and even Alaska in the summer. Depending on the time of year, they may be ubiquitous in mountain environments like grasslands or landscapes of sagebrush, where trees and shrubs are fairly spread out.
Behavior and ecology
Breeding
The male can be seen singing from bare branches. The singing takes place right at dawn, just when the sun rises.
Mountain bluebirds nest in pre-existing cavities or in nest boxes. In remote areas, these birds are less affected by competition for natural nesting locations than other bluebirds. Mountain bluebirds are monogamous. After the couple decides together on an ideal nesting site, the female will typically build their nest themselves out of thin, dry material from the surrounding landscape while the male protects the area, defending against unwelcome visitors. It is true, though, that both males and females fiercely protect the nest. Once the nest is built, the female will lay an egg a day. Eggs are pale blue and unmarked, sometimes white. The clutch size is four or five eggs and she will incubate them for about two weeks. Young are naked and helpless at hatching and may have some down. The young will usually take about 21 days before they leave the nest, and it can take up to two months to raise fledglings to a stage of development at which they are able to fend and provide for themselves.
Mountain bluebirds are cavity nesters and can become very partial to a nest box, especially if they have successfully raised a clutch. They may even reuse the same nest, though not always. These birds will not abandon a nest if human activity is detected close by or at the nest. Because of this, they can be easily banded while they are still in the nest. The threats of predation for those that dwell in nesting boxes are mostly from house cats, raccoons, and the parasitic blowfly, Apaulina stalia.