Birds are guided by their natural tastes in selecting their food, unless driven 

 by necessity. Of the food which suits their tastes that which is most easily taken 

 is usually first selected. In the main, species of similar structure and habits often 

 choose similar food, but each species usually differs from its allies in the selection 

 of some certain favorite insects. Were a species exterminated, however, its place 

 might be taken eventually by the combined action of many species, for nature 

 always operates to restore her disturbed balances. 



The complexity of the food relations existing between birds and other 

 organisms may be indicated hypothetically by a brief illustration. The eagles, 

 larger hawks and owls feed to some extent on crows, and probably the nocturnal, 

 tree-climbing, nest-hunting raccoon also robs them of eggs and young; otherwise, 

 they seem to have very few natural enemies to check their increase. Crows feed 

 on so many different forms of animal and vegetable life that they are nearly 

 always able to find suitable food ; therefore they are common and widely dis- 

 tributed. 



There are compensations in the apparently destructive career of the crow. 

 An omnivorous bird, it seems inclined to turn its attention to any food which is 

 plentiful and readily obtained. It is a great feeder on May beetles (miscalled 

 "June bugs"), the larvae of which, known as white grubs, burrowing in the ground, 

 sometimes devastate grass lands and also injure the roots of many plants, includ- 

 ing trees. 



The crow is also a destroyer of cutworms. These are the young of larvae 

 of such noctuid moths or "millers" as are commonly seen fluttering from the 

 grass by any one who disturbs them by walking in the fields. Robins also feed 

 largely on cutworms, as well as on the white grub of the May beetle. When these 

 insects are few in number, a part of the usual food supply of both robin and 

 crow is cut off. This being the case, the hungry crows are likely to destroy more 

 young robins and other young birds than usual, in order to make up the supply 

 of animal food for themselves and their ravenous nestlings. In a few years this 

 would decrease perceptibly the number . of robins and other small birds, and 

 would be likely in return to allow an increase of May beetles and cutworms. As 

 the insects become more plentiful the crows would naturally turn again to them, 

 paying less attention to the young of robins and other birds for the time, and 

 allowing them to increase once more, until their multiplication put a check on 

 the insects, when the crows would of necessity again raid the robins. 



The blue jay may be taken as another instance of this means of preserving 

 the balance of nature. Hawks and owls kill blue jays, crows destroy their eggs 

 and young; thus the jays are kept in check. Jays are omnivorous feeders. They 

 eat the eggs and young of other birds, particularly those of warblers, titmice 

 and vireos — birds which are active caterpillar hunters. But jays are also 

 extremely efficient caterpillar hunters. Thus the jays compensate in some 

 measure for their destruction of caterpillar-eating birds. Like the crow, they 



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