A History of North American Birds, Land Birds. Volume 1. Robert Ridgway
a decided shade of green. The fore part of breast, the throat and chin, pale brownish-yellow; rest of lower parts white; the sides washed with brownish-olive. Sides of the throat and fore part of the breast with sub-rounded spots of well-defined brown, darker than the back; the rest of the breast (except medially) with rather less distinct spots that are more olivaceous. Tibiæ yellowish-brown. Broad ring round the eye, loral region, and a general tinge on the side of the head, clear reddish buff. Length, 7.00; wing, 4.15; tail, 3.10; tarsus, 1.10.
Hab. Eastern North America; westward to Humboldt Mountain and Upper Columbia; perhaps occasionally straggling as far as California; north to Slave Lake and Fort Yukon; south to Ecuador and Brazil. Cuba, Gundlach; Costa Rica, Lawr.
Specimens examined from the northern regions (Great Slave Lake, Mackenzie River, and Yukon) to Guatemala; from Atlantic States to East Humboldt Mountains, Nevada, and from intervening localities. The extremes of variation are the brownish-olive of eastern and the clear dark greenish-olive of remote western specimens. There is no observable difference between a Guatemalan skin and one from Fort Bridger, Utah.
Habits. The Olive-backed Thrush, or “Swamp Robin,” has very nearly the same habitat during the breeding season as that of the kindred species with which it was so long confounded. Although Wilson seems to have found the nest and eggs among the high lands of Northern Georgia, it is yet a somewhat more northern species. It does not breed so far south as Massachusetts, or if so, the cases must be exceptional and very rare, nor even in Western Maine, where the “Ground Swamp Robin” (T. pallasi) is quite abundant. It only becomes common in the neighborhood of Calais. It is, however, most widely distributed over nearly the entire continent, breeding from latitude 44° to high Arctic regions. It winters in Guatemala and southward as far as Ecuador and Brazil.
In its habits this thrush is noticeably different from the T. pallasi, being much more arboreal, frequenting thick woods; rarely seen, except during its migrations, in open ground, and seeking its food more among the branches of the trees.
Mr. Ridgway found this species very abundant among the Wahsatch Mountains, where it was one of the most characteristic summer birds of that region. It was breeding plentifully in the cañons, where its song could be heard almost continually. It inhabited an intermediate position between T. auduboni and T. fuscescens, delighting most in the shrubbery along the streams of the cañons and passes, leaving to the T. auduboni the secluded ravines of the pine regions higher up, and to the T. fuscescens the willow thickets of the river valleys. He did not meet with it farther west than the East Humboldt Mountains. The song, in his opinion, resembles that of the Wood Thrush (T. mustelinus) in modulations; but the notes want the power, while they possess a finer and more silvery tone.
The song of this species has a certain resemblance to that of T. pallasi, being yet quite distinct, and the differences readily recognized by a familiar ear. It is more prolonged; the notes are more equal and rise with more regularity and more gradually, are richer, and each note is more complete in itself. Its song of lamentation when robbed of its young is full of indescribable pathos and beauty, haunting one who has once heard it long after.
When driven from the nest, the female always flies to a short distance and conceals herself; making no complaints, and offering no resistance.
These birds, in a single instance, have been known to reach Eastern Massachusetts early in April, in an unusually early season, but they generally pass north a few weeks later. They make no prolonged stay, and are with us rarely more than three or four days. Their return in the fall appears to be, at times, by a more inland route. They are then not so numerous near the coast, but occasionally are abundant.
Their nests in Nova Scotia, wherever observed, were among the thick woods, on horizontal branches of a forest-tree, usually about five feet from the ground. Those observed in the Arctic regions by Mr. Kennicott were frequently not more than two feet from the ground.
The nests average about four inches in diameter and two in height, the cavity being three inches wide by about one and a half deep. They are more elaborately and neatly constructed than those of any other of our thrushes, except perhaps of T. ustulatus. conspicuous among the materials are the Hypnum mosses, which by their dark fibrous masses give a very distinctive character to these nests, and distinguish them from all except those of the T. ustulatus, which they resemble. Besides these materials are found fine sedges, leaves, stems of equisetaceous plants, red glossy vegetable fibres, the flowering steins of the Cladonia mosses, lichens, fine strips of bark, etc.
The eggs, which are four or five in number, exhibit noticeable variations in size, shape, and shades of coloring, bearing some resemblance to those of T. ustulatus and to the eggs asserted to be those of T. nanus, but are sufficiently distinct, and are still more so from those of T. aliciæ. They range in length from .83 to .94, with a mean of .88, their mean breadth is .66, the maximum .69, and the minimum .63. Their ground color is usually bluish-green, sometimes light blue with hardly a tinge of green, and the spots are of a yellowish-brown, or russet-brown, or a mixture of both colors, more or less confluent, with marked variations in this respect.
Turdus ustulatus, Nuttall, Man. I, 1840, 400 (Columbia River).—Baird, Birds N. Am. 1858, 215, pl. lxxxi, fig. 1.—Ib. Rev. Am. B. 1864, 18.—Cooper & Suckley, P. R. Rep. XII, II, 1860, 171.—Ridgway, Pr. A. N. S. Philad. 1869, 127.—Dall & Bannister, Tr. Chic. Acad.—Cooper, Birds Cal., 5.
Sp. Char. General appearance of fuscescens, but with pattern of swainsoni; the buff orbital ring as conspicuous as in latter. The olive above is more brown than in this, and less yellowish than in fuscescens, becoming decidedly more rufescent on wings and less observably so on tail. Pectoral aspect different from fuscescens, the spots narrower and cuneate, sharply defined, and arranged in longitudinal series; in color they are a little darker than the crown. Length, 7.50; wing, 3.75; tail, 3.00; tarsus, 1.12.
Hab. Pacific Province of United States. Tres Marias Isl., Guatemala (winter), Mus. S. I.
This well-marked race is to be compared with swainsoni, not with fuscescens, as has generally been done; the latter, except in shade of colors, it scarcely resembles at all; still greater evidence that such is its affinity is that the T. ustulatus builds its nest on a tree, and lays a spotted egg, like swainsoni, while fuscescens nests on or near the ground, perhaps never in a tree, and lays a plain blue egg. The song of the present bird is also scarcely distinguishable from that of swainsoni. Upon the whole, we see no reason why this should not be considered as a Pacific Province form of the Turdus swainsoni; at least it becomes necessary to do so, after referring to T. pallasi as geographical races, the T. auduboni and T. nanus.
Habits. So far as we are aware, this thrush has a very limited distribution, being mainly restricted to the Pacific coast region from California to Alaska in the breeding season, though migrating southward in winter to Guatemala. Dr. Kennerly found it in great abundance breeding at Chiloweyuck Depot, July 3, 1859. Dr. Cooper also found it one of the most abundant of the summer residents in Washington Territory, arriving there in May and remaining until the beginning of September. Three specimens of this thrush were obtained at Sitka, by Mr. Bischoff. Mr. Ridgway met with only a single specimen east of the Sierra Nevada, though on that range he found it an abundant summer bird.
In its general appearance it has a marked resemblance to Wilson’s Thrush (T. fuscescens), but its habits and notes, as well as its nest and eggs, clearly point its nearer affinity to Swainson’s Thrush (T. swainsoni), its song being scarcely different from that of the latter species. Like this species, it frequents the thickets or brushwood along the mountain streams, and, except just after its arrival, it is not at all shy. In crossing the Sierra Nevada in July, 1867, Mr. Ridgway first met with this species. He describes it as an exquisite songster. At one of the camps, at an altitude of about 5,000 feet, they were found unusually plentiful. He speaks of their song as consisting of “ethereal warblings,—outbursts of wild melody.” “Although its carols were heard everywhere in the depth of the ravine, scarcely one of the little musicians could be seen.” “The song of this