6;6 



BIRDS. 



directions are combiner!. The raising of the wing after each stroke 

 requires relatively little effort, the resistance to be overcome being 

 very slight. In steering, the feathers of the tail often bear to the 

 wings a relation comparable to that between rudder and sail. 



FIG. 376. Wings coming down. From Marey. 



Modes of flight. There are three chief modes of flight : 

 i. By gliding or skimming, during which the bird has its wings 

 spread, but does not flap them, depending for its movement on the 



FIG. 377. Wings completely depressed. From Marey. 



velocity acquired by previous strokes, by descending from a highei 

 to a lower level, or by the wind. This may be readily observed in 

 gull and heron, in a pigeon gliding from its loft to the ground, or in 

 a falcon swooping upon its quarry. 



