Chap. 36 



BIRDS — CONQUEST OF THE AIR 



C 

 A 



741 



Fig. 36.12. Pigeons (Columba) photographed during a take-off for flight with 

 exposures of 1/825 second. A, front and B, rear view with wings together. C, 

 nearly, and D, at the bottom of the downstroke; note the slight rotation and for- 

 ward movement of the wing. E and F, wings during the upstroke; in F the 

 feathers have opened and the wings move backward, their motions faster than on 

 the downward stroke. (After Aymar. Courtesy, Young: The Life of the Verte- 

 brates. Oxford, England, The Clarendon Press, 1950.) 



in claws; so do the first and second fingers of the ostrich. Ancient birds had 

 such claws and used them in climbing. After making several downward and for- 

 ward strokes birds often hold their wings motionless and glide. Before a high 

 wind a bird can flex its wings and glide with the wind. Usually, at high eleva- 

 tions, it rises through the air and soars in circles without moving the wings, 





'] 



A 



Standing 



Fig. 36.13. Standing and stepping. Drawings from photographs of a goose. 

 A, standing; B, stepping. In stepping the center of gravity is brought over the foot 

 on the ground by a rotation of the femur on the tibia (Fig. 36.10, knee). The 

 tail is shifted to the left. A similar human gait is associated with weight and cer- 

 tain moods. (After Heinroth.) 



