Birds of America 
(State Bird of Idaho and Nevada)
By John James Audubon, F. R. SS. L. & E.
VOLUME II.
ARCTIC BLUE-BIRD.
[Mountain Bluebird.]
SIALIA ARCTICA, Swains.
[Sialia currucoides.]
PLATE CXXXVI.--MALE AND FEMALE.
This beautiful species, first introduced to the notice of ornithologists by Dr. RICHARDSON, who procured a single specimen at Fort Franklin in July 1825, is merely a summer visitor to the Fur Countries. Both the male and the female are represented in my plate. The latter I believe has not hitherto been figured. Mr. NUTTALL'S notice respecting this interesting bird, so closely allied to Sialia Wilsoni, is as follows:
"Sialia arctica. Ultramarine Blue-bird. About fifty or sixty miles north-west of the usual crossing place of that branch of the Platte called Larimie's Fork, in the early part of June, this species of Sialia is not uncommon. The female utters a low plaint when her nest is approached, the place for which is indifferently chosen in a hole in a clay cliff, or in that of the trunk of a decayed cedar. At this time the young were hatched. The nest is made of the usual material of dry grass in very insignificant quantity. They are more shy than the common species, and have the same mode of feeding by watching on some low bush or plant, and descending for an insect. We afterwards saw a nest of this species on a cliff of the Sandy river, a branch of the Colorado of the West. The female and male were both feeding their brood. The former chirped and appeared uneasy at my approach, and at intervals uttered a plaintive yeow. The male sings more quaintly and monotonously than the common kind, but in the same general tone and manner."
To this Mr. TOWNSEND adds that it is found in the "Forests on the banks of the Platte river, in the vicinity of the Black Hills, and in the same situations on the banks of the Columbia. This species," he continues, "was observed in the winter at Fort Vancouver, associating with S. occidentalis. They confine themselves chiefly to the fences in the neighbourhood of the Fort, occasionally flying to the ground, and scratching in the earth for minute insects, the fragments of which were found in their stomachs. After procuring an insect, the male usually returned to the fence, and warbled for a minute most delightfully. Its note, although like that of our common Sialia, is still so different as to be easily recognised. It is equally sweet and clear, but of so little power (at least at this season) as to be heard only at a short distance. In the spring it is louder and bolder, but is at all times much less strong than that of the common species."
ERYTHACA (SIALIA) ARCTICA, Arctic Blue-bird, Swains. and Rich. F. Bor. Amer., vol. ii. p. 209.
ARCTIC BLUE-BIRD, Sialia Arctica, Nutt. Man., vol. ii. p. 573.
ARCTIC BLUE-BIRD, Sylvia Arctica, Aud. Orn. Biog., vol. v. p. 38.
Adult Male.
Bill of ordinary length, nearly straight, broader than high at the base, compressed towards the end; upper mandible with the dorsal line straight and declinate, until near the end, when it becomes convex, the ridge narrow, the sides convex towards the end, the edges direct and overlapping, with a distinct notch close to the narrow deflected tip; lower mandible with the angle of moderate length and narrow, the dorsal line straight, the sides convex, the edges direct, the tip narrow. Nostrils basal, oval.
Head rather large; neck short; body moderately full. Feet of ordinary length, slender; tarsus compressed, covered anteriorly with seven long scutella, posteriorly with two very long plates meeting so as to form a sharp edge; toes of moderate length; the first stouter, the second and fourth nearly equal, the third much longer; claws moderate, well curved, slender, compressed, laterally grooved, tapering to a fine point.
Plumage soft and blended, with considerable gloss; short bristles at the base of the upper mandible. Wings very long; the first quill very small, being only seven-twelfths of an inch long, the second one-twelfth shorter than the third, which is longest, but exceeds the fourth only by half a twelfth, the other primaries rapidly graduated; the outer secondaries emarginate, the inner not elongated. Tail long, deeply emarginate, of twelve strong feathers, of which the medial are five-twelfths shorter than the lateral.
Bill and feet black; iris brown. The general colour of the upper parts is light azure blue, approaching to smalt blue; the quills and larger coverts dark greyish-brown, the outer tinged with blue, the primaries broadly margined with light blue, the secondaries with greyish-blue, the inner chiefly with dull white. The tail-feathers are also brown, gradually more blue toward the base, and all broadly margined externally with that colour. The sides of the head, the fore part and sides of the neck, and the anterior half of the breast, light greenish-blue; that colour gradually fading on the hind part of the breast; the abdomen and lower tail-coverts greyish-white.
Length to end of tail 7 1/4 inches; bill along the ridge 6/12, along the edge of lower mandible (7 3/4)/12; wing from flexure 4 (7 1/2)/12; tail 2 11/12; tarsus (10 1/2)/12, hind toe 4/12, its claw 4/12; middle toe (7 1/2)/12, its claw (2 3/4)/12.
Adult Female.
The female differs greatly. The parts which retain the same colour are the rump, wings, and tail, of which, however, the blue edgings are less pure and of less extent, and the outer primary and outer tail-feathers are margined externally with white. The upper part of the head, the hind neck, the back, scapulars, and wing-coverts are light greyish-brown, margined with pale greenish-blue; the cheeks and sides of the neck are paler; the fore part of the neck and the anterior portion of the breast are light greyish-brown, on the breast tinged with red; the rest of the lower parts of an undecided brownish-white tint; the lower wing-coverts pale greyish-brown, edged with white, the lower tail-coverts with a medial dusky streak.
Length to end of tail 6 3/4 inches; bill along the ridge (6 1/2)/12; wing from flexure 4 2/12; tail 2 7/12; tarsus 10/12; hind toe 4/12, its claw (4 1/4)/12, middle toe (6 3/4)/12, its claw (3 1/4)/12.
The above descriptions are taken from skins procured by Mr. TOWNSEND on the Columbia river. That of the male is from a specimen shot in June 1835; and that of the female from one shot on the 26th of the same month and year. Of two other specimens in my possession, a male agrees with that described, but has the blue of the upper parts deeper, and of a tint approaching to that of the common species. The female is also similar to that described, but has a dull white spot before, the eye, and the upper part of the throat brownish-white.