PLUMAGE CHANGES OF THE COCK GROUSE 37 



of the month. The rump and back are now completely covered with new 

 black - centred feathers carrying broad - barred buff and black bands, and a 

 few have a whitish terminal spot, similar to that found in the female. The 

 head and neck, breast and throat, are now clothed in broad - barred buff 

 and black feathers, quite distinct from the more chestnut and more finely 

 black-marked plumage of the winter. It is impossible on seeing a series of 

 the birds showing this distinctive change to avoid noticing how closely this 

 autumn plumage of the cock approximates to the nesting plumage of the hen, 

 and yet it is wrong to think and to speak of this "autumn" plumage as 

 an " eclipse " plumage, for it has arrived in the cock just two months later 

 than it is normally due in the hen far too late to be a breeding plumage. 

 It appears almost as though the pathological postponement of the moult, 

 a postponement which is, after all, nothing but a sign and a symptom of 

 disease, has gradually developed into a normal habit in the life of p oss jbi e 

 the bird, and one is led to think that this habitual disability in the postpone- 

 cock Grouse, which results from Strongylosis during the nesting, ment - 

 courting, and breeding season (a disability which causes the death of about 

 eight cocks to every hen in April and in May), may have caused the altera- 

 tion in the season of the moult, simply because the vis vitce of the cock 

 bird, insufficient as we now know it to be at the close of winter for the 

 ordinary calls of reproduction, would be still more disastrously insufficient 

 if preceded by an early moult. 



At the present time the cock undoubtedly breeds in the winter plumage, 

 without any further acquisition of new feathers, and, as has recently been 

 pointed out by Mr Ogilvie-Grant, what have been regarded by Mr Millais 

 as new "spring feathers" on the neck are in fact the old autumn feathers, 

 which on that part of the body do not become worn and faded. 



That any feather of the Grouse, either in the cock or in the hen, was 

 ever altered as to its pigment either in pattern, or in tone, or in change in 

 any other character, when once it had completed growth and had {JJS^b. 

 been cut off from the circulation, is at present an assumption which able- 

 is not well supported by the physiology of feather growth. 



Metchnikoff's observation upon the migration of leucocytes into hair and 

 their action in removing pigment cannot for one moment be adduced as 

 conclusive proof that the same thing may happen in the case of a full-grown 

 feather. While the circulation is active in the feather shaft, and for as long 



