Hab. United States, from Rocky Mountains to Pacific coast.
In the present bird the bill is darker in color, much smaller, and more depressed, the depth at the base being less than the width, instead of being equal to it as in var. gilvus. The wing is more rounded, the second quill much shorter than the sixth, generally shorter or but little longer than the seventh. In var. gilvus, the second quill is about equal to the sixth. The second quill is about .30 of an inch (or more) shorter than the longest in swainsoni, while in gilvus it is only about .20 shorter. The feet of swainsoni are weaker, and the colors generally paler and grayer. The iris, according to Coues, is dark brown.
Young birds in autumnal plumage have the crown decidedly ash, the sides more greenish; the wing-coverts pass terminally into a light brownish tint, producing an inconspicuous band.
Habits. This Western representative of the Warbling Vireo is found throughout the western portions of our Union, from the Great Plains to the Pacific, and from Arizona to the extreme northern boundary of Washington Territory.
Dr. Cooper characterizes this as a lively and familiar songster. It arrives, he states, at San Diego about April 10, and reaches Puget Sound toward the middle of May, occupying nearly all the intermediate country throughout the summer. It frequents the deciduous trees along the borders of streams and prairies, coming into gardens and orchards with familiar confidence, wherever cultivation has reclaimed the wilderness. Like its Eastern prototype, its cheerful and varied song is heard all day long until quite late in the autumn. They too build their nests in the shade-trees of the parks of busy cities, singing ever their delightful strains, unconscious of the busy and noisy crowd that throngs the neighboring streets.
Dr. Cooper states that its nests are pendent from the forks of a branch high above the ground, sometimes to the height of a hundred feet.
Mr. Ridgway, who observed the habits of this species in Utah and Nevada, speaks of it as the characteristic Vireo of the West. It was found by him in all the fertile localities, and was one of the most common birds in the wooded regions. He found it very generally distributed through the summer, inhabiting the copses along the streams of the mountain cañons, and the open groves of the parks, as well as the cottonwoods and willows of the river valleys. In the fall the berries of a species of the cornel that grows along the mountain streams constitute its principal food. Its notes and manners are identical with those of the Eastern species.
The nests of this species are not distinguishable, except in the necessarily varying materials, from those of the Eastern birds. In position, size, and shape they are the same. The eggs, four or five in number, are white, spotted with brown and reddish-brown, and measure .78 by .58 of an inch. The spots are somewhat darker than those of the V. gilvus, and the shape more of an oblong-oval, in all that I have seen. But this difference may disappear in the examination of a larger number.
A nest found by Mr. Ridgway near Fort Churchill, Nevada, June 24, was suspended from the extremity of a twig of a sapling of the cottonwood, in a copse of the same growing in a river-bottom. It has a height of two and a half inches, and a diameter of three. It is composed externally of an elaborate interweaving of spiders’-webs, willow and cottonwood down, and strong cord-like strips of fine inner bark. These are strongly bound around the twigs from which the nest is suspended. It is one of the most elaborately interwoven, homogeneous, and well-felted nests of this bird I have ever met with. Another nest, from Parley’s Park, Utah, obtained June 28, differs in having the external portion woven almost exclusively of fine strips of bleached bark, and is lined with fine wiry grasses. In each of these the eggs were four in number, all oblong-oval in shape, but much more pointed at one end in the latter nest.
This species was found breeding in Napa Valley, Cal., by Mr. A. J. Grayson, and at Fort Tejon by Mr. Xantus.