FORM AND HABIT: THE FEET. 29 
Sparrows use both feet in searching for food, jumping 
quickly backward and throwing the leaves behind them, 
Parrots use their foot as a hand. Some Hawks carry 
nesting material in it, and all birds of 
prey strike their quarry with their { 
strongly curved claws, which are then 
used to carry, or hold it while it is 
being torn by the bill. The foot of 
the Fish Hawk is a magnificent organ. 
The nails are strong and well curved ; 
the inner surface of the toes is set with 
sharp, horny spikes, and the outer toe 
is partly reversible, so that the bird 
grasps its slippery prey from four dif- 
ferent points. Fie, 15.—Foot of Fish 
} : Hawk, showing large 
As a weapon the foot is especially claws, and spicules on 
effective, the use of spurs being too oe aba ben 
well known to require comment. Os- _ 
triches kick with their feet, and can, it is said, deliver a 
blow powerful enough to fell a man. 
But by far the best instance of modification in the 
structure of the feet is furnished by Grouse. It is an 
Fro. 16.—Naked toes of Ruffod Grouse in summer; fringed toes of Ruffed 
Grouse in winter. (2/, natural size.) 
unusual case of seasonal adaptation in form. During the 
summer the toes of Grouse are bare and slender, but as 
