HAB. Central table-lands of North America, east to mouth of Yellowstone. One individual collected at Fort Franklin, Great Bear Lake. Not common on the Pacific slope; the only specimens received coming from Simiahmoo, Fort Crook, and San Diego. Not recorded as found in Mexico. W. Arizona, COUES. As already stated, the blue of this species is greener, more smalt-like than in _sialis_. The females are distinguished from those of the other species by the greener blue, entire absence of rufous, and longer wings. In autumn and winter the blue of the male is much soiled by amber-brown edges to the feathers, this most conspicuous on the breast, where the blue is sometimes almost concealed; the plumage of the female, too, at this season is different from that of spring, the anterior lower parts being soft isabella-color, much less grayish than in spring. HABITS. This Bluebird belongs chiefly to the Central fauna, and occupies a place in the Eastern only by its appearance on its borders. It was first procured by Sir John Richardson, at Fort Franklin, in July, 1825. It is abundant throughout the central table-lands of North America, between the Pacific and the mouth of the Yellowstone, from Great Bear Lake to the lower portions of California. In the latter State it is not common. Mr. Nuttall met with this species in the early part of June, northwest of Laramie Fork. The female uttered a low complaint when her nest was approached. This was constructed in a hole in a clay cliff. Another was found in the trunk of a decayed cedar. In one of these the young were already hatched. The nest was composed of dried grasses, but in very insignificant quantity. Mr. Nuttall found them much more shy than the common species, and describes them as feeding in very nearly the same manner. He afterwards found a nest of the same species in a cliff of the Sandy River, a branch of the Colorado. Both parents were feeding their brood. The female was very uneasy at his approach, chirping, and at intervals uttering a plaintive cry. He states that the male bird has a more plaintive and monotonous song than that of the common Bluebird, and that it has the same warbling tone and manner. He afterwards observed the same species in the winter, at Fort Vancouver, associating with the Western Bluebird. Dr. Woodhouse found the Arctic Bluebird quite common in the vicinity of Santa Fé, in New Mexico, where they breed about the houses in boxes put up for them by the inhabitants for the purpose. Mr. Townsend found this species in the vicinity of the Platte River, near the Black Hills, and also on the banks of the Columbia. They confined themselves to the fences in the neighborhood of settlements, occasionally lighting upon the ground and scratching for minute insects. He describes their song as a delightful warble. Its notes resemble those of the common Bluebird, but are so different as to be easily recognized; they are equally sweet and clear, but have much less power.