As in the others, the colors of this species are much duller in fall and winter. No. 53,319, ♂ (Carson City, Nevada, Feb. 21) differs from others in the following respects: there is hardly any chestnut on the back, there being only just a tinge along each side of the interscapular region; that on the breast is interrupted in the middle, and thrown into a patch on each side of the breast, thus connecting the blue of the throat and abdomen; the blue of the throat is unusually deep. HABITS. This Bluebird belongs to western North America, its proper domain being between the Rocky Mountains and Pacific, from Mexico to Washington Territory. Mr. Nuttall first met with this species among the small rocky prairies of the Columbia. He speaks of its habits as exactly similar to those of the common Bluebird. The male is equally tuneful throughout the breeding-season, and his song is also very similar. Like the common species he is very devoted to his mate, alternately feeding and caressing her and entertaining her with his song. This is a little more varied, tender, and sweet than that of the Eastern species, and differs in its expressions. Nuttall describes this as an exceedingly shy bird, so much so that he found it very difficult to obtain a sight of it. This he attributes to the great abundance of birds of prey. Afterwards, in the vicinity of the village of Santa Barbara, Mr. Nuttall again saw them in considerable numbers, when they were tame and familiar. Dr. Cooper states that these Bluebirds seem to prefer the knot-holes of the oaks to the boxes provided for them. He does not confirm Mr. Nuttall’s description of its song, which he regards as neither so loud nor so sweet as that of the Eastern species. He describes it as a curious performance, sounding as if two birds were singing at once and in different keys. Many of this species remain in Washington Territory during the winter, where Dr. Cooper met with them in December. They associated in flocks, frequented roadsides and fences, and fed upon insects and berries. Dr. Gambel found this species throughout the Rocky Mountains, and always in company with the _Sialia arctica_, being by far the more abundant species. Dr. Kennerly mentions finding this species very abundant during his march up the Rio Grande. Through the months of November, December, and January they were always to be seen in large flocks near small streams. The Western Bluebird constructs a nest usually of very loose materials, consisting chiefly of fine dry grasses. These are not woven into an elaborate nest, but are simply used to line the hollows in which the eggs are deposited. Near San Francisco Mr. Hepburn found a pair making use of the nest of the _Hirundo lunifrons_. On another occasion the Bluebirds had not only taken possession of the nest of this swallow, but actually covered up two fresh eggs with a lining of dry grasses, and laid her own above them.