64 BIRD FRIENDS 



the results of its work and to educate the public as to 

 the value of birds. 



Since its formation, the Bureau has collected a 

 large mass of facts regarding the food habits of over 

 four hundred species of birds and has published the 

 results of its investigations in bulletins printed by 

 the Government, some given away, others sold at 

 nominal prices. Some conception of the work of the 

 Bureau may be gained by looking over the partial 

 list of bulletins given on pages 318-19. This work 

 has steadily grown in importance and to-day the 

 Bureau is one of the most serviceable divisions of 

 the Department of Agriculture, employing eleven 

 men in the work on economic ornithology. 



Methods of determining food of birds. Three 

 methods have been used to determine the food hab- 

 its of birds : (1) field observations of living birds to 

 observe the kinds of foods taken and the amounts; 

 (2) study of birds kept in captivity; (3) examina- 

 tion of the contents of birds' stomachs after the birds 

 have been killed. 



Field observations. In order to determine a bird's 

 food from a study of the living bird, it is necessary 

 to get close to the bird or use a pair of field-glasses, 

 and even then it is difficult to determine exactly the 

 specific nature of the food. This method can best be 

 used in studying the food of nestlings. The parents 

 bring food frequently to the same spot and one is 

 able to approach close to the nest. Some observers 



