ADAPTATION OF STRUCTURE TO HABITS. 
235 
them all: it is thick and close, reaching down to the very 
toe-nails; the change it undergoes in colouring is very 
curious, and is peculiar to this bird. In winter the plumage 
of the Ptarmigan is snowy white, with the exception, in the 
male, of a dark line over the eye, and the twelve outer tail- 
feathers, which are black, as also the beak. In summer 
the livery of the male is brown or blackish, excepting the 
pinion and belly feathers, which are white; that of the 
female is rusty yellow, intermingled with wavy lines of a 
darker hue. The use of this garment is evident; it is 
the creature’s best protection. In winter it so closely 
resembles the snow as to defy the scrutiny of the sharpest 
Falcon; in summer it perfectly assimilates to the colour 
of the ground in the locality where it lives, for the white 
pinion feathers remain hidden under the wing-coverts so 
long as the bird is on the ground, being only exposed in 
the act of flying. This conformity of colouring is just as 
important for the protection of the bird as is the con¬ 
struction of its feet to enable it to seek its food. The 
unassuming Ptarmigan rarely suffers for the want of the 
above; there are occasions, however, when searching for 
food is accompanied with some difficulty. A deep snow¬ 
storm covers the earth, while alternate thaws and frosts 
form an icy crust, which renders this occupation a labo¬ 
rious task, requiring instruments especially adapted for 
the purpose. The Ptarmigan is provided with them in the 
shape of long broad nails; and, thanks to these natural 
shovels, which are annually renewed,* is enabled to dig 
deep runs, or galleries, under the snow, and thus obtain 
access to its old feeding-grounds. 
With Gallinaceous birds the foot is the principal 
instrument; with others, whose plumage resembles in 
* The author distinctly states that the nails are annually renewed. 
2i 
