Brownish yellow, with transverse black bars, (summer); or pure white, (winter); shafts of the quills, and lateral tail-feathers, always black.
T. rupestris, Sab. Supp. Parry s First Voy. p. cxcv. Richards. App. Parry s Second Voy. p. 348. Faun. Bor. Amer. pt. 2. p. 354. pi. 64. T. Lagopus, Temm. Man. d'Orn. torn. 11. p. 468. Rock Ptarmigan, Shaw, Gen. Zool. vol. xi. p. 290.
Entire length fourteen inches: length of the bill (from the forehead) seven lines, (from the gape) one inch; of the tarsus one inch four lines and a half; of the tail four inches; of the wing seven inches. Faun. Bor. Am.
Smaller than the last species, with the bill longer and narrower. Winter plumage exactly similar. Summer plumage characterized by its brownish yellow colour, with rather broad blackish brown bars, exhibiting none of the cinereous tint which predominates in the Common Ptarmigan: on the upper parts the black markings prevail over the yellow; on the under the yellow ground is most conspicuous: primary and secondary quills, with some of the coverts, white; the shafts of the quills black: tail with the two middle feathers barred like the back; the rest black, faintly tipped with white. The male is at all seasons distinguished from the female by a black band across the eye, as in the last species: in its summer plumage, it is furthermore characterized by having the middle of the belly white. (Egg). Bufiy white, nearly covered with spots of two shades of dark red brown: long. diam. one inch nine lines; trans, diam. one inch two lines.
This species, originally described by Pennant, (Arct. Zool. vol. 11. p. 364. no. 184). occurs in North America, and very plentifully in some parts of the Continent, but has been confounded by Temminck and others with the Common Ptarmigan. In Great Britain, it has hitherto only occurred once. This specimen was killed in Perthshire in Scotland, and is now in the collection of Lord Derby. Is said to frequent dry rocky grounds, and to feed on the tops of small birch. Hatches in June.