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

Чтение книги онлайн.

      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. Some Mexican specimens, being in winter plumage, have the breast more buffy than Northern (spring or summer) examples, and the rufous of the head, etc. is somewhat brighter.

      In aliciæ, no difference is observed between Eastern and Western birds; the reason is, probably, that the breeding-ground of all is in one province, though their migrations may extend over two. There is, however, a marked difference between the spring and autumn plumage; the clear grayish of the former being replaced, in the latter, by a snuffy brown, or sepia tint,—this especially noticeable on wings and tail.

      PLATE I.

      1. Turdus mustelinus, Gm. Pa., 1570.

      2. Turdus ustulatus, Nutt. Oregon, 2040.

      3. Turdus aliciæ, Baird. Illinois, 10084.

      4. Turdus swainsoni, Cab. Penn., 981.

      5. Turdus fuscescens, Steph., D. C., 28231.

      6. Turdus pallasii, Cab. Penn., 2146.

      7. Turdus nanus, Aud. Cala., 17997.

      8. Turdus auduboni, Baird. Rocky Mts., 10886.

      The following synopsis is intended to show the characters of the different species and varieties.

1. Spots beneath rounded, covering breast and sides

      A. Rufous brown above, becoming much brighter toward the bill, and more olivaceous on the tail. Beneath white; whole breast with rounded spots. Nest on tree; eggs pale blue.

      1. T. mustelinus. Beneath nearly pure white, with rounded blackish spots over the whole breast, sides, and upper part of abdomen; wing, 4.25; tail, 3.05; culmen, .80; tarsus, 1.26. Hab. Eastern Province United States, south to Guatemala and Honduras. Cuba and Bermuda of West Indies.

2. Spots beneath triangular, on breast only

      B. Entirely uniform in color above,—olivaceous, varying to reddish or greenish with the species. Beneath whitish, with a wash of brownish across the breast and along sides. СКАЧАТЬ