CENTROCEECUS UEOPHASIANUS, SAGE COCK. 



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Bo&.— Sage plains of the West. East to Western Kansas. South to about 35°. West 

 and north as far as suitable surface extends. Scarcely to be found on the Missouri. 



Zist of specimens. 



Lieutenant TTarren's Expedition. — No. 5419, fifty miles up the Yellowstone ; 8921, 8923, 

 Cheyenne Eiver. 



Later Exjjeditions.—GOiG^, Le Bont(5 Creek; 60826-32, Wyouiing; 61096-9, Henry's 

 Fork ; 62223-5, North Fork and Henry's Lake, Idaho. 



The above extensive suite of specimens illustrates this sijecies under 

 the various conditions of age, sex, and season, from the downy young 

 to the largest cocks. The measurements given show the variation iu 

 size among adult birds. Some old cocks are of great size — the birds 

 apparently growing, in some instances, after they have attained normal 

 dimensions. The female, as usual, is smaller than the male, averaging 

 about one-third less. There is no occasion to describe the bird minutely 

 in the present connection; its great size and various peculiar features 

 will prevent mistake respecting it. The full-grown cocks average about 

 2J feet in length; the hens rather under 2 feet. The tail equals, or 

 rather exceeds, the wing in length, and consists of twenty very narrow 

 acuminate feathers, stiiiened and graduated in length from the middle 

 pair outward. A more remarkable feature of the cock is the immense 

 dilatable air-sac of naked yellow skin on each side of the neck, bordered 

 by a patch of tjuriously stiffened, horny feathers, like fish-scales, often 

 terminating in bristly filaments several inches long. The feet are feath- 

 ered to the toes, as iu most of our other Grouse. The most noticeable 

 color-mark is a broad black area on the under parts of the adult, 

 less extensive in the lemale; it contrasts witli the white of the breast. 

 The upper parts are varied with gray, black, brown, and tawny or 

 whitish. The cocks weigh from three to six pounds, according to age 

 and condition ; the hens are correspondingly much lighter. 



The history of this species is generally dated from the account by 

 Lewis and Clarke, of a "Cock of the Plains" which they found in the 

 Rocky Mountains, about the headwaters of the Missouri, and afterward 

 more abundantly on the plains of the Columbia. The first technical de- 

 scription of the species was that of Bonaparte, who, under the name of 

 Tetrao urophasianus, noticed in various periodicals, and figured in his 

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