HOW A BIRD FEEDS. 49 



and the plover is the same, as the nature of their 

 food is the same ; though differing in the form 

 and way it is procured. The beak has changed to 

 enable it to obtain the same kind of food in a 

 form inaccessible except to a beak specially modi- 

 fied for its capture. But the digestive organs of 

 the plover, the ostrich, and the hawk, are very 

 different, because the food they have to digest is 

 different. 



A detailed discussion on the digestive apparatus 

 of a bird would be out of place here. Suffice it to 

 say that it may be divided into four parts — a 

 mouth, a gullet, down which the food passes 

 from the mouth ; a gizzard or stomach in which 

 the breaking-up and digestion of the food is be- 

 gun, and the intestines in which the process of 

 digestion is completed, and from which it is 

 taken by the blood into the body to build up 

 the tissues spent in work. 



In many birds, such as the pigeon and common 

 fowl, the gullet is provided with a large thin-walled 

 bag, called the crop. Into this considerable quan- 

 tities of food arc taken, to be used later. No 

 digestion takes place here, but the food is softened 

 by admixture with saliva ; it is mostly a storehouse 

 used by birds that have to take in much food at 

 a time, and then retire to assimilate it. Dur- 

 ing this process of gathering the daily bread the 

 bird is exposed to many enemies ; thus an advan- 

 tage is gained if it is able to take in a large store 

 rapidly, and then retire slowly to digest it. In 

 the same way bullocks, antelopes and sheep, have 

 developed a remarkable stomach, which enables 

 them to lay in rapidly a large quantity of food, 

 D 



