A History of North American Birds, Land Birds. Volume 1. Robert Ridgway

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СКАЧАТЬ Mackenzie River. In the latter regions it was found breeding abundantly. It was also found in large numbers on the Anderson River, but was rare on the Yukon, as well as at Great Slave Lake, occurring there only as a bird of passage to or from more northern breeding-grounds.

      In regard to its general habits but little is known. Dr. Coues, who found it in Labrador, breeding abundantly, speaks of meeting with a family of these birds in a deep and thickly wooded ravine. The young were just about to fly. The parents evinced the greatest anxiety for the safety of their brood, endeavoring to lead him from their vicinity by fluttering from bush to bush, constantly uttering a melancholy pheugh, in low whistling tone. He mentions that all he saw uttered precisely the same note, and were very timid, darting into the most impenetrable thickets.

      This thrush is a regular visitant to Massachusetts, both in its spring and in its fall migration. It arrives from about the first to the middle of May, and apparently remains about a week. It passes south about the first of October. Occasionally it appears and is present in Massachusetts at the same time with the Turdus swainsoni. From this species I hold it to be unquestionably distinct, and in this opinion I am confirmed by the observations of two very careful and reliable ornithologists, Mr. William Brewster of Cambridge, one of our most promising young naturalists, and Mr. George O. Welch of Lynn, whose experience and observations in the field are unsurpassed. They inform me that there are observable between these two forms certain well-marked and constant differences, that never fail to indicate their distinctness with even greater precision than the constant though less marked differences in their plumage.

      The Turdus aliciæ comes a few days the earlier, and is often in full song when the T. swainsoni is silent. The song of the former is not only totally different from that of the latter, but also from that of all our other Wood Thrushes. It most resembles the song of T. pallasi, but differs in being its exact inverse, for whereas the latter begins with its lowest notes and proceeds on an ascending scale, the former begins with its highest, and concludes with its lowest note. The song of the T. swainsoni, on the other hand, exhibits much less variation in the scale, all the notes being of nearly the same altitude.

      I am also informed that while the T. swainsoni is far from being a timid species, but may be easily approached, and while it seems almost invariably to prefer the edges of the pine woods, and is rarely observed in open grounds or among the bare deciduous trees, the habits of the T. aliciæ are the exact reverse in these respects. It is not to be found in similar situations, but almost always frequents copses of hard wood, searching for its food among their fallen leaves. It is extremely timid and difficult to approach. As it stands or as it moves upon the ground, it has a peculiar erectness of bearing which at once indicates its true specific character so unmistakably that any one once familiar with its appearance can never mistake it for T. swainsoni nor for any other bird.

      The nests measure about 4 inches in diameter and 2¾ in height. The cavity is 2 inches deep, and its diameter 2½ inches. They are unusually compact for the nest of a thrush, and are composed chiefly of an elaborate interweaving of fine sedges, leaves, stems of the more delicate Equisetaceæ, dry grasses, strips of fine bark, and decayed leaves, the whole intermingled with the paniculated inflorescence of grasses. There is little or no lining other than these materials. These nests were all found, with but few exceptions, on the branches of low trees, from two to seven feet from the ground. In a few exceptional cases the nests were built on the ground.

      Occasionally nests of this species are found constructed with the base and sides of solid mud, as with the common Robin (Turdus migratorius). In these, as also in some other cases, their nests are usually found on or near the ground. So far as I am aware neither its occasional position on the ground, nor its mud frames, are peculiarities ever noticeable in nests of T. swainsoni.

      The eggs were usually four in number. Their color is either a deep green tint, or green slightly tinged with blue; and they are marked with spots of russet and yellowish-brown, varying both in size and frequency. Their mean length is .92 of an inch, and their mean breadth .64. The maximum length is .94 and the minimum .88 of an inch. There is apparently a constant variation from the eggs of the T. swainsoni; those of the aliciæ having a more distinctly blue ground color. The nests are also quite different in their appearance and style of structure. The Hypnum mosses, so marked a feature in the nests of T. swainsoni, as also in those of T. ustulatus, are wholly wanting in those of T. aliciæ.

      This bird and the robin are the only species of our thrushes that cross the Arctic Circle to any distance, or reach the shore of the Arctic Ocean. It occurs from Labrador, all round the American coast, to the Aleutian Islands, everywhere bearing its specific character as indicated above. It is extremely abundant on and near the Arctic coast, between the mouth of the Mackenzie River and the Coppermine, more than 200 specimens (mostly with their eggs) having been sent thence to the Smithsonian Institution by Mr. MacFarlane. In all this number there was not a single bird that had any approach to the characters of T. swainsoni, as just given. From the Slave Lake region, on the other hand, T. swainsoni was received in nearly the same abundance, and unmixed during the breeding season with T. aliciæ.

Turdus swainsoni, CabanisOLIVE-BACKED THRUSH; SWAINSON’S THRUSH

      Turdus swainsoni, Cab. Tschudi, Fauna Peruana, 1844-46, 188.—? Sclater & Salvin, Ibis, 1859, 6 (Guatemala).—Sclater, P. Z. S. 1858, 451 (Ecuador); 1859, 326.—Ib. Catal. 1861, 2, No. 11.—Baird, Birds N. Am. 1858, 216; Rev. Am. B., 1864, 19.—Gundlach, Cab. Jour. 1861, 324 (Cuba).—Ib. Repert. 1865, 229.—Pelzeln, Orn. Brazil. II. 1868, 92 (Marambitanas, Feb. and March).—Lawr. N. Y. Lyc. IX, 91 (Costa Rica).—Ridgway.—Maynard.—Samuels, 152.—Cooper, Birds Cal. 6.—Dall & Bannister. Turdus minor, Gmelin, Syst. Nat. I, 1788, 809 (in part). Turdus olivaceus, Giraud, Birds L. Island, 1843-44, 92 (not of Linn.). (?) Turdus minimus, Lafresnaye, Rev. Zoöl. 1848, 5.—Sclater, P. Z. S. 1854, 111.—Bryant, Pr. Bost. Soc. VII, 1860, 226 (Bogota).—Lawrence, Ann. N. Y. Lyc. 1863. (Birds Panama, IV, No. 384.)

      Sp. Char. Upper parts uniform olivaceous, with 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 СКАЧАТЬ