DESTROYERS OF INSECT PESTS 71 



to keep down their numbers. Such a constant check 

 are the birds, which constitute one of Nature's most 

 effective means of controlling insects and keeping a 

 proper balance. Parasitic and predaceous insects 

 are another means of keeping the balance. The 

 birds work from sunrise till sunset devouring in- 

 sects during the warmer months of the year when 

 insects are abundant, and some birds during the 

 winter feed on insects' eggs and on the hibernating 

 insects. 



Man's disturbance of Nature's balance. Nature 

 when left to herself has balanced these forces evenly, 

 so that the insects are kept by birds and other 

 natural checks from becoming excessively numer- 

 ous and destructive. But man has upset Nature's 

 balance in many ways. First, new crops have been 

 introduced; second, forests have been cleared and 

 crops raised on larger areas, thus furnishing more 

 food for insects and allowing them to increase; 

 third, many insects have unwittingly been intro- 

 duced into the United States from other countries; 

 and fourth, most strange and unbelievable of all, 

 man has wantonly destroyed the birds, Nature's 

 check on the increase of injurious insects. 



Service performed by the birds. The great service 

 that birds and other insect-enemies are now render- 

 ing to man is in destroying enough insects so that the 

 remainder will not do excessive and uncontrollable 

 damage. The birds can never utterly destroy any 



