A History of North American Birds, Land Birds. Volume 1. Robert Ridgway
of bill, and nearly two and a half times length of gonys. Legs weak; tarsi rather longer than middle toe and claw. Tail feathers tapering slightly from base to near tip, giving a slightly cuneate appearance to the tail.
Turdinæ. Bill stouter, more lengthened; narrow at base and more compressed; width at base less than distance from nostril to tip; commissure not more than twice distance from nostrils to tip of bill, and about twice length of gonys. Tarsi stouter, longer than middle toe and claw. Tail feathers widening slightly from base to near tip, giving a parallel-sided or slightly fan-shaped appearance to the tail.
The Miminæ differ, as already mentioned, in the scutellate tarsi: more rounded wings, etc.—S. F. B.
Subfamily TURDINÆ
There are several American genera of Turdinæ not found north of Mexico as yet, although it is not impossible that one of these (Catharus) may hereafter be detected within the limits of the United States. The species of Catharus resemble the North American wood-thrushes (Hylocichla); but the spurious or first primary quill is longer (from one half to one third the second quill), the wings are rounded, not pointed, the tarsus is longer than the head, and the outstretched toes extend beyond the tail. The species to be looked for are C. melpomene and occidentalis.22
The North American species of Turdinæ, while retained under the single genus Turdus, yet constitute several distinct groups, which we may call subgenera.
Turdus, Linnæus, Syst. Nat., ed. 10, 1758, 168. (Type, Turdus viscivorus of Europe.)—Baird, Rev. Am. Birds.
Gen. Char. Bill conical, subulate, shorter than the head; the tip gently decurved and notched (except in Hesperocichla); the rictus with moderate bristles; the wings rather long and pointed, with small first primary (less than one fourth the second); wings considerably longer than the tail, which is firm, nearly even, with broad feathers. Tarsi variable, seldom as long as the skull, the scutellæ fused into a continuous plate, only in rare individual instances showing indications of the lines of separation.
The genus Turdus is very cosmopolitan, occurring nearly throughout the globe, excepting in Australia, and embraces species of highest perfection as singers. In the large number of species known there are many variations in external form, but the transition from one to the other is so gradual as to render it very difficult to separate them into different genera. The sections of the group we adopt are the following:—
Hylocichla. Smallest species. Bill short, broad at base; much depressed. Tarsi long and slender, longer than middle toe and claw, by the additional length of the claw; outstretched legs reaching nearly to tip of tail. Body slender. Color: above olivaceous or reddish, beneath whitish; breast spotted; throat without spots.
Turdus. Bill stouter and higher. Tarsi stout and short, scarcely longer than middle toe and claw. Body stout, generally whitish beneath and spotted. (Second quill longer than fifth?)
Planesticus. Similar to preceding. (Second quill shorter than fifth?) Beneath mostly uni-colored; unstreaked except the throat, which is whitish with dark streaks.
Merula. Similar to Turdus. Male usually more or less black, especially on the head; females brownish, often with streaked throats. Bill distinctly notched.
Hesperocichla. Similar to Turdus. Male reddish beneath, with a black collar. Bill without notch.
Hylocichla, Baird (s. g.), Rev. Am. Birds, 1864, 12. (Type, Turdus mustelinus.)
Turdus mustelinus.
1570
The essential characters of Hylocichla have already been given. The subgenus includes the small North American species, with Turdus mustelinus, Gm., at the head as type, which are closely connected on the one side with Catharus, by their lengthened tarsi, and with Turdus by the shape of the wing. The bills are shorter, more depressed, and broader at base than in typical Turdus, so much so that the species have frequently been described under Muscicapa.
It is not at all improbable that naturalists may ultimately conclude to consider the group as of generic rank.
In this group there appears to be five well-marked forms or “species.” They are, mustelinus, Gm., pallasi, Caban., fuscescens, Steph., swainsoni, Caban., and aliciæ, Baird. The first-named is totally unlike the rest, which are more closely related in appearance.
In studying carefully a very large series of specimens of all the species, the following facts become evident:—
1. In autumn and winter the “olive” color of the plumage assumes a browner cast than at other seasons; this variation, however, is the same in all the species (and varieties), so that in autumn and winter the several species differ from each other as much as they do in spring and summer.
Turdus ustulatus.
Of these five species, two only (pallasi and swainsoni) inhabit the whole breadth of the continent; and they, in the three Faunal Provinces over which they extend, are modified into “races” or “varieties” characteristic of each region. The first of these species, as the pallasi var. pallasi, extends westward to the Rocky Mountains, and migrates in winter into the South; specimens are very much browner in the winter than in spring; but in the Rocky Mountain region is a larger, grayer race, the var. auduboni. This, in its migrations, extends along the central mountain region through Mexico to Guatemala; specimens from the northern and southern extremes of this range are identical in all the specific characters; but the southern specimens, being in the fall and winter dress, are browner in color than northern ones (spring birds); an autumnal example from Cantonment Burgwyn, N. M., is as brown as any Central American specimen. Along the Pacific Province, from Kodiak to Western Mexico, and occasionally straggling eastward toward the Rocky Mountain system, there is the var. nanus, a race smaller than the var. pallasi, and with much the same colors as var. auduboni, though the rufous of the tail is deeper than in either of the other forms. In this race, as in the others, there is no difference in size between specimens from north and south extremes of its distribution, because the breeding-place is in the North, all Southern specimens being winter sojourners from their Northern birthplace.
The T. swainsoni is found in abundance westward to the western limit of the Rocky Mountain system; in the latter region specimens at all seasons have the olive of a clearer, more greenish shade than in any Eastern examples; this clearer tint is analogous with that of the Rocky Mountain form of pallasi (auduboni). In precisely the same region inhabited by the pallasi var. nanus the swainsoni also has a representative form,—the var. ustulatus. This resembles in pattern the var. swainsoni, but the olive above is decidedly more rufescent,—much as in Rocky Mountain specimens of T. fuscescens; the spots on jugulum and breast are also narrower, as well as hardly darker in color than the back; and the tail is longer than in Rocky Mountain swainsoni, in which latter it is longer than in Eastern examples. The remaining species—mustelinus, fuscescens, and aliciæ—extend no farther west than the Rocky Mountains; the first and last only toward their eastern base, while the second breeds abundantly as far as the eastern limit of the Great Basin.
The T. fuscescens, from the Rocky Mountains, is considerably darker in color above, while the specks on the throat and jugular are sparser or more obsolete than in Eastern birds.
In T. mustelinus, the only two Western specimens in the collection (Mount Carroll, Ills., and Fort Pierre) have the rump of a clearer grayish than specimens from the Atlantic Coast; in all other respects, however, they appear to be identical.
See Baird, Review American Birds, I, 1864, 7, 8.