THE VERTEBRATES: BIRDS 



231 



tinctive as to give much aid in determining the identity of 

 birds in nature. Note the flight of the woodpeckers; it 

 identifies them unmistakably in the air. Note the rapid 



('' " .'I'M '»',' ' 'i • 



riff' ' 



Fig. 123. The yellow - hammer, Colaptes auratus. (Photograph from 

 life by W. E. Carlin; permission of G. O. Shields.) 



beating of the wings of quail and grouse; also of wild ducks; 

 the slow, heavy, flapping of the larger hawks and owls, and 

 of the crows; and the splendid soaring of the turkey-buzzard 

 and of the gulls. This soaring has been the subject of much 

 observation and study, but is still imperfectly understood. 



