deferred moult becomes in some years almost the rule, and the rule of health becomes almost the exception. It is a very difficult matter, Effects of
disease. indeed, for any one who has not had the opportunity of examining an extensive series of Grouse skins, in disease as well as in health, and covering every month of the year, to come to any true conclusion about the moult. Diseased conditions often entirely mask the normal plumage changes from time to time, and it is far more important to realise this than to examine thousands of more or less healthy birds shot in the ordinary course of events in the shooting season. A study of abnormal plumage changes in diseased Grouse is essential if the discrepancies which arise in the moult of what are often wrongly considered normal birds, are ever to be explained. Once this point is grasped the question becomes much simpler, and it is because the Grouse Disease Committee has had such ample opportunity for studying both sides of the question that it has been deemed necessary to enter into these plumage changes at such length.
It is almost incredible that a moult should be deferred from one season to another, or even to a third, and that the right plumage should eventually be produced if the bird, by means of good food and good weather, is at Effect of
feet and
legs. 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 a natural accompaniment of really good health, while thickly feathered legs in the same month are a sure sign of deferred moult and of sickness. It is only when the proper season for the moult of the leg and foot-feathering is completely understood that we begin to understand the reason for attaching an unfavourable prognosis to heavy leg-feathering when the legs should have been featherless, and an equally favourable prognosis to bare legs when the legs should certainly have been bare (PI. xiii., Figs. 1-2).
To return, however, to the two plumages of the healthy cock Grouse. They are distinguished by Mr Ogilvie-Grant as the autumn plumage and the winter-summer plumage, and he says further that the cock "has no distinct summer plumage."[1] It is perfectly easy to see what is meant by this, and also by the statement which follows, that the cock "retains the winter plumage throughout the breeding season."
- ↑ "Handbook to the Game Birds," p. 28. (Allen's Naturalists' Library). London: W. H. Allen & Co., Ltd., 1895.
