8 USEFUL BIRDS. 



All animals and plants are sustained and nourished by 

 air, water, and food. Food supplies the material for growth 

 and development. Its abundance increases the energy and 

 fertility of a species, its ability to produce young abun- 

 dantly. The study of the food and food habits of birds and 

 other animals is of the utmost importance, for by this study 

 alone we are enabled to trace their life relations to each 

 other, to plants, and to man. Some progress has already 

 been made in this study. We know in a general way the 

 character of the food of some of the common birds of the 

 United States ; but we know so little as yet of the food of 

 the smaller mammals, the reptiles, batrachians, many insects 

 and other lower animals, that it is impossible to tell what 

 may be the ultimate effect of the destruction of any one of 

 these animals by birds. 



On the other hand, no one can tell what grave and far- 

 reaching results might follow the extermination of a single 

 species of bird ; for it is probable that the food preferences 

 of each species are so distinctive that no other could fill its 

 place.. 



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-haunting 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 distributed. 



