ON THE CHANGES OF PLUMAGE IN THE RED GROUSE 137 



on the other hand, when the weather is comparatively open 

 and mild, a few feathers of the mantle may still be found in 

 quill as late as the middle of December, by which time the 

 male bird has not only passed through his autumn change, 

 but also completed his winter moult. The food supply 

 being much greater in mild weather, no doubt accounts for 

 the bird being apparently unable to continue its moult in 

 very cold weather when food is comparatively scarce. 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 September. 

 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 go through the much 

 less exhaustive process of redecorating their old autumn 

 feathers and making them serve the purpose of new summer 

 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 Grouse is similar to what takes place on 

 the sides and flanks, but very much more complete, all the 

 feathers being widely barred with black and yellowish buff 

 by the beginning of May (Plate VI. Fig. 12). It will be 

 easily understood that the fore neck and chest being con- 

 spicuous 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 complete. The greater part of this 

 change is generally produced by moult ; but, as is the case in 

 the flank feathers, some individuals (probably less robust 

 females) attain the greater part of the change without a 

 moult. The same rearrangement of the pigment described 



