most favorable for man, as for other mammals. And man's use of the forest 

 well illustrates the effects of his interference with the balance of nature. The 

 settlers cleared land as rapidly as possible to make room for farms and homes. 

 Much of the wood they used to construct shelters, barns, fences, bridges. 

 Year by year, however, as the population grew and extended westward, for- 

 ests became the source of valuable material which needed merely to be cut and 

 shipped. They were treated like mines that would last forever. 



In the first hundred years after the formation of the Union, timber was so 

 recklessly cut that millions of acres of forests which had taken centuries to 

 grow were destroyed. Since a virgin forest is a well-balanced living com- 

 munity, its growth is at a standstill. New growth is just enough to offset the 

 death and destruction among old trees. When man invades the forest, not 

 only does he remove wood faster than the new growth can replace it, but he 

 destroys also the shelter and food upon which birds and mammals normally 

 depend. As a result, the weeds, insects, and other small animals upon which 

 these birds and mammals feed begin to multiply at a rapid rate, so that the 

 entire community is thrown out of balance. 



Man and Birds Like most animals, birds are important to us chiefly 

 because of the food they eat. But unHke insects, for example, birds in their 

 feeding are usually of advantage to mankind. Many birds have been con- 

 victed of eating fruit in the orchards. And it is true that the sharp-shinned 

 hawk has been caught carrying off young chickens from the barnyard. Never- 

 theless, with a very few exceptions, the common birds are worth more to us 

 alive (as destroyers of insects, vermin and weeds) than dead (as sources of 

 feathers or food) or as objects of sport. 



We cannot class each species of bird as altogether useful or altogether in- 

 jurious. The red- tailed hawk feeds on field-mice in one region and discovers 

 that chickens are good to eat in another. The bobolink is a serious menace to 

 the rice fields in the South, but is a valuable insect destroyer in the North. 

 The red-winged blackbird ate so much grain in Nebraska one year that the 

 farmers took up arms and killed the bird off. The following year, however, the 

 absence of the blackbirds enabled the locusts to multiply so rapidly that many 

 of the grain crops were ruined. 



In Pennsylvania, in the 1880's, the state legislature voted a bounty for 

 killing hawks and owls, which were supposed to be killing chickens. In less 

 than two years nearly $100,000 was paid in bounties. Biologists who studied 

 the situation in detail found that the predatory birds might have killed chick- 

 ens worth a few thousand dollars. But they found further that the mice which 

 birds did not kill damaged the crops to the extent of $4,000,000. The law was 

 repealed. 



Destruction of Birds Many birds are destroyed wantonly by ignorant 

 boys and men. Some are killed to supply feathers. Still others are exter- 



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