PLUMAGE CHANGES OF THE HEN GROUSE 47 



left at the point of detachment of the old nail is quite a useful indication of 



age in cases where there is a doubt as to a bird being over twelve months old or 



of the year. The presence of the groove showing that the claws have once at 



least been shed is conclusive proof that the bird is more than twelve months old. 



In Ju7ie there is another characteristic appearance in the hens, namely the 



bare patch of abdominal skin which results from the shedding of the abdominal 



feathers, grown in the previous September. The loss of these feathers 



leaves a naked patch of skin on the abdomen of a hen that has been on abdo- 

 men. 



sitting, and this patch remains naked for the next few months (PL 

 XIV.). The general character of a June hen in health is that of the completed 

 summer-nesting plumage, broad-barred buff and black over all the upper and 

 under parts, excepting the abdominal area, the lower breast, wings, and tail. 

 But it looks already somewhat faded and worn ; and it is quite probable that in 

 acquiring so perfect a plumage for sitting unnoticed on a nest built amongst the 

 heather, the economic absence of the redder pigment in the feathers is in part 

 a result of the acknowledged fact that for longer and more trying use, and for 

 wear and tear in feathers, darker pigments are required, whereas for the short- 

 lived and less exacting requirements of the summer plumage in the hen Grouse 

 from April to June the buff and black feathers, with very much poorer wearing 

 qualities, are found to be sufficient. The accompanying figures of a few worn- 

 out and moulting feathers taken from a hen in summer plumage, show how 

 distinctly better the black pigmented parts of the feather stand wear and tear 

 than the yellow parts (PI. xv.). Certain pigments have a value, therefore, 

 of a very practical nature apart altogether from the sesthetic point of view 

 of attractiveness, or the rather hypothetical view of assimilation to surround- 

 ings for purposes of safety or to assist in obtaining food. He would be unwise, 

 however, who denied that all three factors play a part in the very beautiful 

 nesting plumage of the hen Grouse. 



It very occasionally happens that the hen Grouse, instead of retaining 

 the redder plumage of the previous autumn's growth on the abdomen until it 

 drops off during incubation, grows an almost universal spring plumage 

 of buff and black broad-barred feathers covering the lower breast sometimes 



absent. 



and abdomen as well as the remainder of the body from head to 

 tail. A skin showing this condition is preserved in the National Collection, 

 and there is an almost equally perfect specimen in the Committee's 

 Collection, No. 919. 



