196 PRINCIPLES OF FARM PRACTICE 



hawk, are known to be harmful. These destroy other birds, 

 and when occasion offers, poultry. Such hawks as the red- 

 tailed and red-shouldered hawks, often called hen or chicken 

 hawks, feed largely upon insects and rodents such as field 

 mice. For example, an examination of the contents of the 

 stomachs of twelve red-shouldered hawks showed that 102 

 mice had been eaten; while only three of 220 stomachs 

 examined contained remains of poultry. Occasionally an 

 individual hawk may get the poultry-eating habit. Such an 

 individual should receive the same consideration as a sheep- 

 killing dog. As a good protection against a hawk getting a 

 taste for poultry, purple martins may be induced by the 

 presence of nesting boxes to guard the poultry yard. The 

 purple martin does not like the hawk and generally succeeds 

 in driving him away. The presence of nesting kingbirds 

 serves the same purpose. 



All of our common owls seem to be beneficial, destroying 

 enormous numbers of insects and harmful mammals. So 

 much cannot be said of the crow. While it destroys many 

 mice and other rodents it also destroys young birds, sometimes 

 poultry, and of ten pulls up corn that is germinating in the fields. 



Food of young birds. Most of our common birds, whether 

 seed-eating or insect-eating, feed their young almost ex- 

 clusively on insects. Young birds grow rapidly and require 

 an abundance of food. Many young birds digest their food 

 in less than two hours. A young bird will often consume 

 food equal to more than one-half its weight in one day. Three 

 young chipping sparrows were kept under observation for 

 an entire day and were seen to receive food from their parents 

 187 times; a family of young martins, 312 times; and a 

 family of wrens, 600 times. 



It happens that the first brood of young birds is produced 



