174 WHITE-TAILED PTARMIGAN. 



often the means of their discovery. In this way they 

 will often reach the opposite edge of the rock, and 

 will, as it were, simultaneously drop off; but the ex- 

 pectation of finding them on some lower ledge will 

 be disappointed, for they have perhaps by that time 

 sought for and reached the opposite side of the moun- 

 tains, by a low, wheeling flight, as noiseless as the 

 solitudes by which they are surrounded. The nest 

 is made under the rocks and stones, and is very diffi- 

 cult to be found, for the female on perceiving a person 

 approach, generally leaves it, and is only discovered 

 by her motion over the rocks, or her low clucking 

 cry. In winter they descend lower, but seldom seek 

 the plains. 



The only other bird belonging to this interesting 

 group is an American species, discovered by the ex- 

 pedition under Captain Franklin. It has the habits 

 of the rest, and inhabits the Rocky Mountains. It 

 has been termed by Dr Richardson Lagopus leucurus, 

 or White-tailed Ptarmigan, and is at once distinguish- 

 ed from any of the rest by the want of black on the 

 pure winter plumage, wanting both the black eye- 

 stripe and black tail, so conspicuous in the others. 

 The summer dress is intermediate in colour between 

 that of the rock and common ptarmigan. 



