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170 GAME BIRDS OF NORTH AMERICA. 



or else remaining motionless, evidently hoping to escape 

 in that way from being seen. But if several are together 

 they will usually take wing, making a great cackling 

 as they rise and fly oflf. 



The flight of this species is firm and well sustained, 

 consisting of a rapid beating of the wings, succeeded by 

 a sailing movement, and can be continued for a long dis- 

 tance; but, as a rule, the birds alight after proceeding 

 for a few hundred yards. The White-tailed Ptarmigan, 

 like its relatives, appears to be continually in moult. It 

 begins to show a few of the blackish brown vermiculated 

 feathers in March, which appear very conspicuously amid 

 the white plumage. The change from out the winter dress 

 is effected very slowly, and the perfect summer plumage 

 is not assumed until about June. In September it begins 

 to change again, the feathers on the under parts being 

 the first that are replaced with white ones. There is no 

 regularity in this moult, as white feathers appear in 

 different parts of the body after the process has once 

 commenced; but it goes on so deliberately that little 

 difference in the bird's appearance is noticeable for some 

 weeks, save perhaps the general hue is somewhat lighter, 

 and it is quite late in the autumn — perhaps, at times, even 

 the middle of winter — before the pure white dress is com- 

 pleted. During all this period of changing plumage no 

 two individuals are alike. The tail remains white all the 

 year round, and renders the bird very conspicuous dur- 

 ing the summer months. 



Although, as I have stated, it is rarely seen in the Cas- 

 cade Mountains in flocks of any size, yet farther south, 

 as in the mountains of Colorado, it associates in com- 

 panies composed sometimes of a hundred individuals or 

 more. This, however, seems to be an aggregation of 

 birds mostly not fully grown, a number of broods con- 



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