WILLOW PTARMIGAN 175 
to the south of latitude 68°, at least in the valley of 
the Anderson.” 
The change of summer plumage to that of winter 
begins on the abdomen and gradually extends over the 
entire body, the head changing last. This change 
occurs between September toth and the last of October, 
the young assuming their winter garb a little in ad- 
vance of the adults. In spring the change is reversed, 
commencing about the head of the birds and thence 
passing over the rest of the body. After the head has 
assumed its summer plumage, the change on the rest 
of the body goes on very slowly, and in many instances 
is never perfected, the back and abdomen of the ma- 
jority of summer specimens being never entirely free 
from white feathers. The wings remain white through- 
out the year. There is considerable individual varia- 
tion in the plumage of adult specimens shot at the same 
season. 
Mr. Charles Sheldon, who spent the winter of 1908 
and 1909 on the shoulders of Mt. McKinley, saw there 
the willow ptarmigan, the rock ptarmigan and the 
white-tailed ptarmigan. These birds were all abun- 
dant, and there was no difficulty at any time in starting 
out and in the course of a short walk killing with 
a .22 rifle a sufficient number to last for food during 
several days. 
In spring, at the mating season, the willow ptarmi- 
gan was extremely noisy, and at that time was seen 
much in the trees, often sitting on the topmost spray, 
from which he uttered his crowing call, and often 
