i86 



ANIMAL BIOLOGY 



arid two behind. Birds which perch generally have toes 

 which automatically close up as the bird settles down upon 

 a limb or perch. 



The jaws of all living species of birds are entirely devoid 

 of teeth and constitute what is known as the beak or 

 bill; this has a tough, horny covering, and varies greatly 

 in shape in different species. Commonly the bill is more or 

 less conical and sharp at the tip, which adapts it for pick- 

 ing up seeds or insects. In birds of prey the bill is curved 



FIG. 145. Bills of birds. I, duck; ia, same from above; 2, gros- 

 beak; 3, spoonbill; 4, snipe; 5, kingfisher; 6, hawk; 7, humming bird; 8 

 crossbill.; . 



downward in front, forming a sort of hook which is used 

 in tearing the flesh of their victims. Ducks, geese and 

 their allies have a flattened bill adapted for scooping up 

 objects in the water or mud. The woodpecker's bill is 

 strong and sharp like a chisel and is used for pecking holes 

 in trees, which is accomplished by a rapid series of strikes 

 the sound of which is familiar to everyone who has been 

 long in the woods. The narrow, slender bill of the hum- 



