328 BIRD BEHAVIOUR 



Blackbird, which gets his black plumage long before 

 his bill turns yellow. 



The iris, like the face and feet, may change colour 

 through emotion ; thus the red eye of a Pochard 

 drake has been seen to change to yellow, no doubt 

 through fear, while he was being handled. Besides 

 changing colour, the horny casing of beak and claws 

 may undergo actual shedding en masse, as distinct 

 from the ordinary gradual wearing. I have already 

 cited the case of the American White Pelican, and 

 may now draw attention to that of our Puffin 

 and of various nearly allied members of the Auk 

 family, in which more or less of the horny sheath of 

 the bill comes off in large pieces after the breeding 

 season, producing in the larger-beaked forms a 

 most remarkable change of appearance, for in the 

 PuiEn the bill, shorn of its nuptial plating, is quite 

 ordinary in size and shape. 



Among the Grouse, the Ptarmigans lose in 

 spring the exaggerated overgrowth of horn on the 

 claws which they acquired in autumn to fit them 

 for winter's snow-shovelling in search of browse ; 

 and the more ordinary Grouse such as Blackgame 

 and Capercailzie also shed the horny fringes to 

 the toes which served in winter to provide a kind 

 of snow-shoe. Even weapons are shed seasonally 

 in at least one instance, that of the Pheasant- 

 tailed Ja9an^, which loses its wing-spurs as well 

 as its long tail after the breeding season. 



