INSECTS AND BIRDS. 



315 



cious rodents, such as house rats and mice, field mice, 

 wood mice and gophers. 



Many hawks and owls feed largely on injurious in- 

 sects. It has been estimated that a single species of 

 hawk saves the western farmers more than $57,600 

 annually during the grasshopper season. It is histori- 

 cal that certain species of field mice increase enor- 

 mously wherever their natural enemies are not suffi- 

 ciently numerous to check them. These irruptions of 



WOODCOCK. 



field mice always prove destructive to vegetation, but 

 they are usually checked by the migration of hawks, 

 owls and other birds that feed on them, and that as- 

 semble in flocks for that purpose. Even the eagles, 

 though in many cases destructive to farm stock, are 

 often valuable in destroying vermin. 



The Protection of Useful Birds. The farmer is 

 usually so situated that he can readily protect many 

 species of birds upon his farm. He can also attract 

 the birds by feeding them, putting up bird houses and 

 nesting boxes, or by planting or preserving wild plants 

 which furnish birds' food. The study of friendly 



