1910.] PLUMAGE OF THE RED GROUSE. 1001 



vexed question of moult and plumage-changes in the Red Grouse, 

 and their proper interpretation. 



Without referring in detail to the points upon which 

 differences of opinion have before now arisen, it may be shown 

 that much misunderstanding upon such a difficult subject as this 

 is based upon a difterent rendering of facts into words, i\icts which 

 wei'e recognized and pei'fectly well explained by Mi'. Ogilvie- 

 Grant in 1893. Both he and Mr. Millais have made the subject of 

 plumage-changes in the game-birds, and especially in the Gi'ouse, 

 a special study, and it must be admitted that there are very few 

 points upon which they have touched which seem to require 

 further explanation ; and still fewer points, if any, which can be 

 brought to light for the first time in connection with the pkunage- 

 changes of the Red Grouse. A monograph on the Red Grouse, such 

 as the Report of the Grouse Disease Inquiry, would, however, be 

 obviously incomplete without an account of the plumage -changes of 

 the bii'd itself ; and it so happens that during the past six years of 

 the Grouse Disease Inquiry's existence the collection of some six 

 hundred Red Grouse skins, representing every age, phase and 

 change of plumage in that bird, has given a unique opportunity 

 for an independent revision of the work already done — an oppor- 

 tunity such as has never occiirred before in the study of any 

 single species of British bird for observing the etfect of disease 

 upon moult and feather-growth. So it happens that although 

 the work as it stands has been so nearly completed by the labours 

 of the two ornithologists already mentioned, there are still points 

 of interest to which attention may be drawn, esj)ecially in con- 

 nection with the marked effect which parasitism and other wasting 

 diseases have upon the moult and growth of feathers ; and it 

 is to this influence of disease that attention will be particularly 

 drawn in the present paper. 



It is almost incredible that a moult should be deferred from 

 one season to another or even to a thii'd, and that the right 

 plumage should eventually be produced if the bird by means of good 

 food and good weather is at last enabled to recover its health and 

 grow any new feathers at all. It is interesting and to some 

 people, such as sportsmen and gamekeepers, even useful to know 

 that bare featherless legs and feet, which have so long been 

 considered a sure sign of disease in the Red Grouse, may, in 

 certain months of the year, be an unavoidable accompaniment of 

 really good health, while thickly feathered legs in the same month 

 are a sure sign of deferred moidt and of sickness. It is only when 

 the proper season for the moult of the leg and foot-feathering is 

 completely understood, that w^e can begin to understand the 

 reason for attaching an unfavoura1)le prognosis to heavy leg- 

 feathering when the legs should have been featherless, and an 

 equallv favourable prognosis to bare legs when the leijs should 

 certainly have been bare (Pis. XCII. & XCIII.). 



To return, however, to the two jjlumages of the healthy cock 

 Grouse. They are distinguished by Mr. Ogilvie-Gi'ant as the 



