First quill spurious; not quite half the second, which is about equal to the eighth; third and fourth quills longest; fifth scarcely shorter. Tail nearly even, or a little rounded, the feathers narrow.
Total length, 4.20; wing, 2.18; tail, 1.90; tarsus, .75.
Hab. United States, from Missouri River to base of Rocky Mountains; Tehuantepec, Mexico (October, Sumichrast); Missouri (Hoy); Iowa (Allen); Southeast Illinois (Ridgway).
The above description is taken from a type specimen received from Mr. Audubon, and represents the average spring plumage. Autumnal skins are rather brighter, and there is occasionally an ochraceous tinge on the white of the under parts.
This species at first sight appears like a miniature of V. gilvus, the head being almost exactly similar. The back is, however, much brighter olive, the sides and crissum deeper yellow. The superciliary light stripe is shorter. The white markings of the wings are wanting in gilvus. The wing, tail, and feet are entirely different in their proportions.
Habits. This species was first procured by Mr. Audubon’s party in the excursion to the Yellowstone River, in what is now known as Dakota Territory.
In his account of it Mr. Audubon states that it is usually found in the bottom-lands along the shores of the Upper Missouri River, from the neighborhood of the Black Snake Hills, as far as they ascended that river. In its habits he describes it as more nearly allied to the White-eyed Vireo than any other.
Dr. Woodhouse, in his report of the Zuñi River Expedition, mentions finding this species abundant in Texas. Mr. Dresser also speaks of it as not uncommon, during the summer, near San Antonio, and remaining there to breed. He mentions finding a nest on the 2d of July in a wesatche bush near the San Pedro, containing three eggs of this species and one of the Cow-Bunting. Being anxious to procure the parent bird he left it, but on his return the nest had been torn and the Vireo’s eggs smashed. Dr. Heermann found a nest on the Medina about the same time. He describes this nest as beautifully formed of fine grasses, and hung from the small twigs of a tree. The eggs, four in number, were very small, white, with an occasional reddish dot at the larger end. The nest found by Dr. Heermann was attached to the pendent twigs of a willow. The stomachs of these Vireos were found to contain small green caterpillars.
Dr. Coues met with this species near Fort Riley, May 23. It appeared to be quite common, and was found inhabiting thickets and clumps of bushes, like V. noveboracensis, but having a very different song, the peculiarity of which first attracted his attention. Mr. Ridgway found it to be a common summer resident in the thickets and copses of Southern Illinois, especially in the prairie districts. He first met with it on the 8th of June, 1871, on Fox Prairie, in Richland County. His attention was drawn to it by its peculiar song, which has a general resemblance to that of the White-eyed Vireo, having the same odd delivery, but being more sputtering, reminding one somewhat of the song of Troglodytes ædon.
This Vireo appears to have quite an extended distribution during the breeding-season, or from Texas to the Upper Missouri, and even as far as the eastern edge of Southern Illinois. It breeds also as far to the east as Eastern Kansas. Its western limits are not so clearly defined. It was not found by Mr. Ridgway in Nevada or Utah, nor by Dr. Coues in Arizona.