Change of Plumage without Moult 87 



"When the summer feathers are suppHed by moult, they 

 usually begin to make their appearance about the beginning 

 of March, and even when fully grown, may generally be 

 recognized from those produced by change of pattern, by 

 their more regular black and buff barring. The change of 

 pattern without a moult appears to take a long time to 

 become complete, for we find that, though autumn 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 hy moult, 

 no change whatever is visible till about the end of February, 

 when the first new feathers begin to appear, though we 

 have noted a single instance of a summer feather making 

 its appearance as early as the middle of December. 



" There can be no doubt that the male Red Grouse com- 

 pletes his autumn moult much more quickly than the 

 female does, many males being in full autumn plumage by 

 the beginning of September. Possibly this may be ac- 

 counted 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 redecorating 

 their old autumnal 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." 



The possibility of a change of pattern in feathers without 

 a moult was vigorously denied in England, when I mooted 

 the subject in 1873, and more recently Professor J. A. 



