569. 
TETRAONIDA — TETRAONINZ:: GROUSE. 587 
secreting part of the passage is as if covered with fresh paint, soft and sticky, which may be 
rubbed uff before it ‘‘sets” on the shell. Size 1.80 « 1.20. 
L. rupes/tris. (Lat. rupestris, relating to rupis, a rock; rupestrine.) Rock PTARMI@AN. 
Bill slenderer for its length than that of L. albus, its depth at base less than the distance from 
nasal fossa to tip; whole culmen 0.67; bill always black. @ 9, in winter: As in L. albus, 
but a black transocular stripe on side of head. @ 9, in summer: The whole plumage, excepting 
the wings and tail, barred with blackish-brown and brownish-yellow. Rather smaller than the 
Fia. 404. — Willow Ptarmigan, winter plumage, } nat, size. (From Brehm.) 
foregoing. Length 14.00-15.00; wing 7.00-7.50; tail 4.50. Arctic America, not S. to the 
U. 8. Eggs 18-15 or more, like those of Z. albus, but darker and rather smaller; size 
1.70 X 1.18. “The summer plumage is assumed at variable periods of the months of April, 
May, and even in early June, according to the locality. The moult for the summer is usually 
shown first on the head and neck, followed by the lower back, sides, breast, middle back, flanks, 
and abdomen, in the order named. The abdomen and chin are the last areas to show the com- 
plete moult. The parts named also assume, in the order given, the white winter plumage. 
During the time of the summer plumage scarcely a single day passes that the general color of 
the feathers is not modified by the appearance or loss of some feather.” (Turner.) Hence the 
difficulty if not impossibility of establishing races of this species upon color, as the amount of 
barring, vermiculation, or nebulation with dusky, tawny, and gray is incessantly changing in 
