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 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 Reasons for
previous
misunderstanding this difficult subject is based upon a different rendering of facts into words, facts which were recognised and perfectly well explained by Mr. Ogilvie-Grant in 1893.[1] 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 opportunity such as has never occurred before in the study of any single species of Effect of
disease on
plumage
changes. British bird for observing the effect 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, 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" (6), xii., July 1893, pp. 62–65; (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, Pl. v. and vi.
