MAMMALS AND BIRDS OF ALASKA 31 



important part in the settling of northorn Alaska. As a result of 

 their year-round occurrence in the Territory, the white grouse arc 

 held in high regard by old-time residents. 



Probably the most abundant of upland game birds is the willow 

 ptarmigan, which lives in most of th(», willow-grown sections of the 

 Territory and sometimes forms flocks so large as to obscure the sun 

 when they take to the air with a thunderous roar of wings. Flocks 

 of 10,000 to 20,000 haA'e been r(>corded during periods of high popula- 

 tions. The rock ptarmigan (fig. 33), slightly smaller in size, is found 

 at greater elevations, and the white-tailed ptarmigan, not much larger 

 than the domestic pigeon, rarely descends from the extremely high 

 ])eaks. 



n 



F 10064 



Figure 32. — Shearwaters in Bering Sea. (Photo by H. B. Carr.) 



In summer, the ptarmigans are colored various shades of brown 

 and gray, more or less in harmony with the natural background, but 

 in winter the plumage becomes pure white except for the black under- 

 tail coverts in the willow and rock species. Early in fall the flesh of 

 these birds has a delicate flavor as a result of their diet of mountain 

 blueberries, cranberries, and grass seeds, but during the long winters, 

 which force them to subsist almost exclusively on willow buds, the 

 meat becomes quite bitter, although they still afford the lone prospec- 

 tor a welcome change of diet from his monotonous fare of bacon and 

 beans. 



It is unfortunate that the Alaska grouse, includuig ptarmigans, 

 ]:)eriodically die off from epizootic disease. Thus, these birds mcrease 

 to great abundance every 8 to 10 years and then are stricken almost 



