THE VERTEBRATES: BIRDS 



223 



number of broods it rears? Compare the habits of the 

 various breeding species of the locality, and find out if the 

 summer residents have any breeding habits in common as 

 distinguished from the all-year residents. 



Observe the behav- s. 



ior of the birds in 

 courting time. Do 

 the males have "sing- 

 ing contests," as is 

 sometimes reported ? 

 Do they fight with 

 each other? Do the 

 males or females show 

 any differences, at this 

 time, from their more 

 usual plumage ? After 

 mating which bird 

 selects the nesting 

 site ? Are old nesting 

 sites preferred to new 

 ones? If two broods 

 are reared is a new 

 nest built? What are 

 the principal causes 

 of mortality among 

 the eggs and young 

 during the breeding 



Season? What in- FlG - 117 - Razorbill auk and egg. (Drawn 

 . . ,. from photograph made from life.) 



stmcts or habits of the 



parents have direct reference to these dangerous conditions ? 

 What means of protecting the nest are resorted to ? What is 

 the behavior of the parents towards enemies of the young ? 

 The field-study of the birds of a given locality will comprise 

 much observation bearing directly on their distribution or 

 special habitat. Certain birds will be found to be limited to 



