30 THE GROUSE IN HEALTH AND IN DISEASE 



It must, however, be added, that there is hardly a month in the whole year, 

 or a Grouse skin in a collection of many hundreds covering every month of the 

 year, in which one plumage only can be found unmixed with the other. This 

 fact accounts largely for the misunderstanding which at one time existed, but 

 which has now, we hope, been satisfactorily settled, in respect of the whole vexed 

 question of moult and plumage changes in the Eed 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 

 Keasons for t^is difficult subject is based upon a different rendering of facts into 

 mSinder- '^'ords, facts which were recognised and perfectly well explained by 

 standing, jyjj. Qgilvic-Grant in 1893.' Both he and Mr Millais have made the 

 subject of plumage changes in the game-birds, and especially in the Grouse, 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 plumage 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 bird itself ; and 

 it so happens that during the 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 occurred before in the study of any single species of 

 Effect of British bird for observing the effect of disease upon moult and feather 

 piuml'a-e" growth. So it happens that although the work as it stands has been 

 changes. g^ nearly completed by the labours of the two ornithologists already 

 mentioned, there are still points of interest to which attention may be drawn, 

 especially in connection 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 important to note the extraordinary irregularities which so commonly 

 occur in the plumage of the Red Grouse owing to disease, whereby the 



' (1) "Annals and Magazine of Natural History" (G), xii., July 1893, pp. 62-G5 ; (2) "Catalogue of the 

 Birds in the British Museum," vol. xxii. November 1893, pp. 36-38; (3) "Annals of Scottish Natural 

 History," July 1894, pp. 129-140, PI. v. and vi. 



