the Willow grouse and ptarmigan. 33 



feathers, altered in this way, begin to show traces of the coming 

 metamorphosis as early as the beginning of November, the 

 colours are often imperfectly arranged by the end of April. 

 When the summer feathers are supplied entirely by moult, no 

 change whatever is visible in the autumn plumage of the flank- 

 feathers till about the end of February, when the first new 

 feathers begin to appear, though we have noted a single in- 

 stance of one summer feather making its appearance as early 

 as the middle of December. 



There can be no doubt that the male completes his autumn 

 moult very much more quickly than the female does, many 

 males being in full autumn plumage by the beginning of Sep- 

 tember. Possibly this may be accounted for by the resources 

 of the female being more severely taxed than those of the male 

 during the breeding-season. It may very naturally be asked 

 why some females should change their summer flank-feathers 

 by moult, while others are enabled to arrive at the same result 

 by going through the much less exhaustive process of re- 

 decorating their old autumn feathers, and making them 

 serve the purpose of new breeding plumage. This is a difficult 

 question to answer, but it seems natural to suppose that the 

 more vigorous birds gain their summer flank-feathers by moult, 

 while nature has enabled the weaker individuals to obtain the 

 necessary protective nesting plumage by a more gradual and 

 less exhaustive process. 



C. Feathers of the Chest, 



The summer change of the feathers of the fore-neck and 

 chest in the female Red Grouse is similar to that which takes 

 place on the sides and flanks, but is very much more complete, 

 all the feathers being widely barred with black and yellowish- 

 buff by the beginning of May (PL III., Fig. 12). 



As will be easily understood, these being conspicuous parts 

 of the bird when she is sitting on her eggs, it is most important 

 for her that the protective black and buff plumage should be 



Q D 



