40 USEFUL BIRDS. 



save by such checks as may come, in time, through natural 

 causes. 



In view of the dangers threatened by insect increase and 

 voracity, how fortunate it is for the human race that so many 

 counter-checks are provided against the multiplication of 

 these destructive creatures. If we could increase by so much 

 as one per cent, the efficiency of the natural enemies of 

 insects, a large proportion of the loss occasioned by insect 

 injury might be saved. Hence the importance of the study 

 of these natural enemies, among which birds hold a high 

 place. 



THE CAPACITY OF BIRDS FOR DESTROYING PESTS. / 



When we realize the losses that insects are capable of in- 

 flicting, we see at once that birds, in their capacity of insect 

 destroyers, continually operate to prevent the destruction of 

 some of our most important industries. If birds are present 

 in sufficient numbers, they will prevent the excessive increase 

 of any kind of a pest which they will eat. 



The number of birds required to accomplish this highly 

 desirable end need not be very large in comparison with the 

 number of insects ; for each bird can devour an incredible 

 number of insects, and the young birds in the nests require 

 more of this food, in proportion to their size, than do their 

 parents . 



The Digestion of Birds. 



The digestive organs of birds are so constructed and 

 equipped that they can both contain and dispose of a very 

 large quantity of food. The stomachs of many species 

 quickly separate the indigestible portions of the food from 

 the digestible parts, and the former are thrown out of the 

 mouth, thus relieving the stomach of much worthless mate- 

 rial, and enabling the bird immediately to consume more 

 food. The alimentary canal (including the crop, gullet or 

 oesophagus, the first division of the stomach or proventricu- 

 lus, the gizzard, gigerium or second division of the stomach, 

 the intestine and the cloaca) consists of a tube reaching from 

 mouth to anus, conveying the food. The nutritious qualities 

 of the food are drawn off by the lacteals as it passes ; the 



