16 EXTEUNAL PARTS 



CHAPTER III 



THE BILL 



The bills of birds, although et^uipped with neither lips nor 

 teeth, have many offices. They are implements for cutting, 

 handling, and carrying; they are organs of touch or feeling; 

 they contain the nostrils for breathing and smelling. With 

 the possible exception of the legs, no feature of birds is more 

 varied in form, size, or appendages, or is more frequently used 



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in systems of classification. Birds can often be classified into 

 families by noting the peculiarities of the bill alone. It would 

 therefore be well to study this chapter thoroughly before using 

 the " Key to the Families of Birds." 



Parts of the bill. — The two great parts are the upper mandible 

 and the loiver mandible. These consist of projecting skull bones 

 covered by a horny material, usually comprising one piece for 

 each jaw. Both jaws are movable. The lower jaw, in most birds, 

 has a great range of movement, while that of the upper jaw is 

 but slight. In parrots this is reversed, the iipper jaw having 



