1910.] PLUMAGE OP THE RED GROUSE. 1009 



If there are, as has been held, distinct pigments, such, for 

 example, as buff", black, and orange-red, in the various colour- 

 tones of the Red Grouse, it 1>ecomes easier to see that the loss 

 of the red pigment which is utilized for the eggs, leaves the buff 

 and the black in greater quantity for the nesting-season plumage. 

 In the winter all three would once more be available. 



The fat of the nesting hen is distinctly rich in colour, but in 

 no case that we have seen has it resembled the orange-coloured 

 fat which is often seen in overfed Pheasants, and quite commonly 

 in Gulls and Terns which have been feeding on i^ed crustaceans. 

 In these birds the oi-ange-red fat or oil, tints not merely the fat 

 beneath the skin, but the white feathers of the breast and body 

 which often present a beautiful rosy flush. 



The whole question of pigment production and pigment dis- 

 tribution, intimately connected as it is with the question of the 

 excretion of waste products and the deposition of fat both in 

 health and in disease, has not reached a stage which admits of 

 dogmatic statement upon the subject of pattern change in feathers 

 without moult. 



One i-ecognized method of changing a colour-pattei'n in feathers 

 without moult is to be seen in the male of the familiar House 

 Sparrow, which produces a handsome jet-black cravat in the 

 breeding-season, where before was a nondescript greyish throat ; 

 and this it does by the simple process of shedding the grey ends 

 of the feathers, leaving the blacker parts exposed. This method 

 is common among birds, but the Red Grouse has been credited 

 with changing in situ the colour and pattern of the flank -feathers. 

 Now, with still less reason as it seems, the cock bird has been 

 credited by Mr. Millais with achieving his sunnner or breeding- 

 plumage " for the most part, by repigmentation and pattei-n change 

 of most of the winter-feathers below the neck." 



This view cannot be upheld physiologically', and there is much 

 to uphohl the contention that the feathers which are believed to 

 effect this change of pattern without moult, are actually new 

 growing feathers. This can readily be shown by the demonstration 

 of their unshed sheaths. The misleading birds are again in this 

 case the cocks which have been too sick to shed the previous 

 " autumn-plumage," and so are still struggling, and Avith 

 increasing success as the food improves, to produce a " winter- 

 plumage," which they should and would, in health, have achieved 

 in October. 



Ti\at the cock bird should moult the feathers of the legs and 

 feet between March 30th and June 17th is no longer ditticult 

 to understand when the ]5revalence of Strongylosis is fully 

 grasped. No bird is safe from the Nematode infestment, and one 

 is led to think that the majority of cock birds are so b;idly in- 

 fested that they are forced to defei- the autumn-moult which should 

 precede that of the previous winter. It is therefore obvious that 

 between March and June there will be every stage of good or bad 

 leg- and foot-feathering between the newly acquired thick white 



