NATURAL ENEMIES OF BIRDS 



physical health and a progressive development of 

 intelligence from generation to generation. Should any 

 species of creature succeed in increasing abnormally 

 in numbers, the balance of Nature is soon restored, 

 because their enemies, owing to the abundance of food, 

 also increase in proportion. For instance, when 

 insects are numerous, birds have plenty of food for 

 themselves and young, and they, in consequence, 

 become more plentiful. The birds from all the 

 surrounding parts also flock in for a share, and remain 

 so long as there is food for them. 



So it is with other forms of life. When vegetation 

 increases abnormally, the herbivorous animals flock to 

 it and the carnivorous animals follow. The balance 

 of Nature is perfectly adjusted, and swings backwards 

 and forwards like the pendulum of a clock, until man 

 steps in and dislocates the machinery. 



Man kills great numbers of the natural enemies of 

 birds, and it might be considered that as a consequence 

 birds would increase abnormally. Man, however, as 

 a general rule destroys more birds directly and indirectly 

 than all these natural enemies, and counteracts the 

 good he does in destroying some of the enemies of 

 birds. Then again, it must be remembered that the 

 artificial cultivation of plants and domestication of 

 animals provides enormous facilities for the abnormal 

 increase of insects. Therefore a corresponding increase 

 in the number of birds is necessary. Purely insectivorous 

 birds, if not persecuted by man, would fluctuate in 

 numbers in accordance with the abundance or otherwise 

 of insect life. On the contrary, birds which supple- 



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