68 BIED FRIENDS 



Still a fourth method is the combination of field 

 and laboratory work. The birds are studied in the 

 field in those localities where birds are collected for 

 stomach examinations. Facts are gathered relative 

 to the available food-supply for birds; these, in con- 

 nection with the examination of the stomach, show 

 what a bird will eat, what it prefers, and what it 

 refuses. 



Good done by birds. These studies of the food of 

 birds show that they help man in three ways: (1) by 

 eating injurious insects; (2) by eating weed seeds; 

 and (3) by eating mice and other rodents. Another 

 way of minor importance in which the birds are use- 

 ful is in acting as scavengers. 



Harm done by insects. Among insects are found 

 some of man's most common foes. In almost every 

 walk of life, man has to contend with insects. The 

 mosquito and fly carry diseases and thus cause 

 thousands of cases of sickness and death every year. 

 The gardener, the fruit-grower, and the farmer are 

 constantly fighting the insects that prey upon their 

 crops. In the vegetable garden, the cabbage-worm 

 attacks the cabbage; the cucumber-beetle, the vine 

 crops; the potato-beetle, the potatoes. In the fruit- 

 garden, the codling moth damages the apple; the 

 currant-worm, the currant; the white grub, the 

 strawberry. On the farm the army-worm destroys 

 the wheat, and the root-aphis attacks the corn. The 

 elm-beetle and tussock-moth attack shade-trees, 



