636 
U. S. P. E. R. EXP. AND SURVEYS — ZOOLOGY — GENERAL REPORT. 
The male bird in winter is pure white throughout, except fourteen tail feathers, which are 
"black, narrowly tipped with white, and a black line through and behind the eye. The shafts 
of the larger primaries are browne xternally, except along the edges. 
The female is said to be similar, but without the black stripe through the eye. 
A supposed summer specimen of this species, probably a female, has the feathers of the back 
black, with narrow transverse bars of yellowish brown and terminated by white. The brown 
bars are largest on the basal half ; the terminal ones are usually interrupted towards the shaft ; 
the last of all sometimes continuous, and separated from the white tip by black. Much the 
greater exposed portion of the feather is black. Beneath and to some extent on the head the 
brownish bars are lighter and much broader, imparting a yellowish tint. The chin is whitish, 
spotted with black. There is no trace of the black lore. The entire wing, excepting the 
middle coverts and tertials, are white, as is also the middle lore of the belly. The outer web of 
external tail feather is white towards the base. 
A specimen from the northwest coast of America, (8082,) presented by Mr. Gould, and 
perhaps a male of the rock grouse, has the feathers of a chestnut color mottled with black, 
and with little or no white edging. This may, however, be a distinct species, different, as it 
certainly is, from the common willow grouse. 
The differences between the American rock grouse and the willow grouse are to be found in 
the smaller size of the latter, and its slenderer, more elongated bill. The black stripe through 
the eye of the male is not found in the willow grouse in either sex. 
List of specimens. 
Catal. No. 
Age. 
Locality. 
When collected. 
Whence obtained. 
Collected by — 
8082 
8083 
2853 
2854 
2855 
2856 
Northwest coast America . 
do 
Summer 
Winter 
S. F. Baird 

d ° ? 
o 
o 
do? 
do 
do 
do 
do 
LAGOPUS LEUCURUS, Swains on. 
White-tailed Ptarmigan. 
Tetrao (Lagopus) leucurus, Swainson, Fauna Bor. Amer. II, 1831, 356 ; pi. Ixiii. — Nut-tall, Man. II, 1834,612.— 
Ib. I, 2d ed. 1840, 820. 
Tetrao leucurus, Aud. Orn. Biog. V, 1839, 200; pi. 418. 
Lagopus leucurus, Aud. Syn. 1839.— Ib. Birds Amer. V, 1842, 125 ; pi. 302. 
Sp. Ch. — Bill slender. Plumage in summer barred with brownish yellow. In winter pure white, including the tail feathers. 
Length, 13 inches ; wing, 7 ; tail, 4.25. 
Hab. — Northern America to the west. Southward along Rocky mountains to Cochetope Pass in latitude 39°. 
Bill rather slender ; the length from the nasal groove considerably greater than the height of 
both mandibles together. Gonys longer than the width of lower jaw at the end of the lateral 
