CHAPTEE III 



THEIB EFFECT UPON HEAIiTH AND THE WORKS OP MAN 



1. The Number of Birds. 2. Their Destruction of Insects Obnox- 

 ious to Man. 3. Their Effect upon Dikes and Canals. 4. 

 As Scavengers. 



The Number of Birds 



In order to obtain a more than casual under- 

 standing of the effect in bulk of birds upon human 

 society, the Biological Survey of the United States 

 Department of Agriculture instituted, in 1914, 

 a bird census. As it was obviously impossible to 

 make a physical count of every feathered individ- 

 ual in the United States, the department selected 

 a number of average tracts of land upon which to 

 make a study. Included were sections of farm 

 land, villages, marshes, forests, and mountains. 

 A definite count of the birds residing there was 

 to be made. Volunteers were called for from the 

 various rural districts and a great many reports 

 solicited from measured areas. 



The result of this first census was the ac- 

 cumulation at Washington of an enormous amount 



SI 



