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- 



foT-emi- rminta FlG - 15- Foot of Fish 



terent points. 1Iawk? showing large 



As a weapon the foot is especially daws, and spicuies on 



J 7 under surface of toes. 



effective, the use of spurs being too (/> natural size.) 

 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 



FIG. 16. Naked toes of Huffed Grouse in summer; fringed toes of Ruffed 

 Grouse in winter. ( 2 / 3 natural size.) 



unusual case of seasonal adaptation in form. During the 

 summer the toes of Grouse are bare and slender, but as 



