PLUMAGE CHANGES OF THE COCK GROUSE 33 



fully recognised, there will always be misunderstandings upon the moult of 

 this bird, for almost every Grouse in the country is to some extent infested with 

 parasitic worms, and there are years when irregularity of moult is the rule rather 

 than the exception. Moreover, it so happens that in autumn, when birds are 

 being shot in large numbers, the survivors of the two worst months of the year 

 for "Grouse Disease" mortality, that is, the survivors of May and June, are all 

 convalescing ; but they are convalescing with their plumage changes all retarded 

 and put completely out of order and routine. In this way it is possible in 

 September to kill two birds on the same day, both of which have the chestnut- 

 coloured feathers of the winter plumage on the chin and throat ; but upon 

 examination it may be seen that in one bird the edges of these feathers are 

 frayed and worn and the colour faded, showing that they have survived from 

 the previous winter plumage ; whereas in the other bird they are hardly free of 

 the scaly sheaths in which they grew, and are really precocious feathers of the 

 coming winter plumage. This is only one of the many traps which result 

 from the deleterious influence which disease exerts upon a bird's capacity for 

 feather growth and replacement, and so upon the regularity of its moult. 



There is another point to which attention must be drawn before entering 

 upon a systematic description of the monthly changes of feather in the cock 

 Grouse. It is as to whether the autumn plumage of the cock can << Eclipse" 

 be correctly described as an " eclipse " plumage, comparable as it P luma s e - 

 obviously is in character with the spring breeding plumage in the hen, but 

 appearing just two months later and after the breeding season. In each 

 sex the general change from winter to summer may be described as a change 

 from a more richly pigmented, darker, black and chestnut, or rufous-chestnut 

 plumage with rather fine transverse black markings, sometimes almost vermi- 

 culate in character, to a less richly pigmented, paler, buff or rufous-buff or tawny- 

 buff plumage with characteristically broad black bars and transverse markings. 



In each sex, moreover, the characteristic buff and black broad-banded 

 summer plumage is given its special appearance on the dorsal aspect by the 

 growth of feathers with large black centres and a few buff or tawny- buff 

 subterminal bars of considerable width, and a terminal border or spot of the 

 palest buff, which is a very conspicuous feature on the back of most hens, and 

 often only less conspicuous in the cock. In the cock, however, this plumage 

 appears just two months later, and is less beautifully developed than in 

 the hen. 



VOL. i. c 



