COMPARING BILLS. 103 



ticks and other vermin that cling to the legs and hides of cattle 

 in hot countries. 



The opposite of this form, the depressed or flattened bill, is 

 well shown in the duck tribe, some of which have very broad, 

 flat bills. The broadest of these are ridged along the inside 

 with little laminae, or plates, that act like a strainer, holding 

 the selected morsels tight, while the mud and water are 

 drained away. This is a convenience to birds that pick up 

 most of their food under water and must take it without 

 cleansing. The flamingo's bill is furnished with a similar 

 strainer. In spite of its size, the flamingo's bill is extremely 

 light, being made up of a spongy, bony tissue, full of air-cells. 

 Few large bills are as heavy as they look to be, since, unless 

 great strength is needed, the interior of the bill is made up of 

 this cellular or aerated bone, as it is called. 



If you were to draw all the kinds of bills you could imagine, 

 I could agree to match most of them from birds now living 

 in some part of the world. Do you make one that turns 

 down at the tip? You have already seen the long-billed 

 curlew's; and the bills of some of the foreign humming- 

 birds and sun-birds are curved in a quarter-circle at the 

 tip. But if you make one that curves up, we can match that, 

 too, in the avocet, a bird of our shores and prairies, with his 

 tilted bill, and as great an oddity as any. With such a bill 

 one would suppose that any bird must be handicapped in 

 getting a living, yet the avocet seems to fare well. 



" It is a beautiful sight," writes one who knows them, " to 

 see a flock of these birds feeding. Wading along in the shal- 

 lows, the bills are moved regularly from side to side, through 

 the water or mud, with the motion a man makes when mowing, 

 each bird keeping to the side and a little behind the leader, and 

 if the water is deep the head and neck are frequently immersed. 



