THE BIRD'S NEST 39 



" I wonder where the Chimney Swifts lived before 

 there were any chimneys," said Rap, looking across the 

 fields to where an old stone chimney stood the only 

 thing left standing of an old farmhouse. Above this 

 chimney, Swifts were circling in shifting curves, now 

 diving inside it, now disappearing afar in the air. 



" We think they must have lived in hollow trees as 

 the Tree Swallows do now," said the Doctor ; " but 

 when House People began to clear the land they natu- 

 rally cut down the dead trees first, and so the birds 

 moved to the chimneys." 



" I used to call those birds Chimney ' Swallows,' but 

 Olive says they are made more like Hummingbirds and 

 Nighthawks than real Swallows," continued Rap. 



" Nighthawks ? " said Nat. "I thought Olive said 

 Hawks were cannibal birds. How are they relations 

 of Swallows ? " 



" That is a mistake a great many people make," said 

 the Doctor ; " for the Nighthawk is not a real Hawk, 

 but a shy bird, who has a rapid hawk-like flight, 

 though it eats nothing but beetles, moths, and other 

 insects. Hark ! Do you hear that cry high in the 

 air ? " 



" As if something was saying c shirk-shirk ' ? " said 

 Nat. 



" Yes ; that is a Nighthawk on its way home. Look ! 

 he is over us now, and you can see two large white 

 spots like holes in his wings. By these you can tell it 

 from any of the real Hawks." 



" Does he build high up in a tree ? " asked Rap. " I 

 have never found his nest." 



" There is a good reason for that," said the Doctor. 



