CHAPTER XII 



CHANGES IN THE NUMBERS OF BIRDS 



There are certain natural agencies which tend 

 to keep birds in check and prevent their too great 

 increase, and these agencies are necessary to pre- 

 serve the balance of nature, else birds might be- 

 come so numerous as to be harmful. Since the 

 white man came to this country he has been re- 

 sponsible both directly and indirectly for other 

 agencies tending to check bird life. The question 

 naturally arises as to whether all these causes com- 

 bined are tending to reduce bird life to such a mini- 

 mum that extermination of certain species is threat- 

 ened, or their reduction to such small numbers that 

 they are no longer able to keep insects in check. 

 We will first investigate the question as to whether 

 the birds have decreased in numbers, either as re- 

 gards the number of species or the number of in- 

 dividuals. 



Extinct birds. Within the past sixty-five years 

 several species of birds, which were formerly found 

 in some portion of the United States, have become 

 extinct, and the last stages of the extermination of 

 two species are being enacted at the present time. 

 Two species, the great auk, and the Labrador duck, 



