DESTROYERS OF INSECT PESTS 



73 



when the bird is in motion. And the digestive sys- 

 tem is so constructed that it digests very rapidly the 

 bird's food, which is then taken by the blood to the 

 various parts of the body, where its oxidation main- 

 tains the high temperature of the body. Probably 

 the whole process of digestion and assimilation of 

 food may take place in an hour and a half, so that 

 during the day the bird may eat enough food to fill 

 its stomach ten or twelve tunes. The study of birds 

 in the field and the examination of the contents of 

 birds' stomachs show that a bird devours enormous 

 quantities of food. 



Records of field observations of birds are con- 

 densed in the following table. These are taken from 

 the reports of Edward H. Forbush: - 



A few examples of the number of insects found in 

 the stomach of a single bird are given below in the 

 table. These figures are taken from the reports of 

 the Bureau of Biological Survey: 



