20 INTRODUCTION. 



the Heron and the Crane wheel their heavy bodies 

 through the air with a slow but steady flapping of a 

 pair of ample, curving wings, their heads drawn in 

 toward the body, and their long legs following like a 

 rudder. 



It is very evident that the shape of the wings, and 

 the arrangement and texture of the feathers com- 

 posing them, must have a material effect upon the 

 flight of birds. A long, pointed, flat wing, with stiff 

 and close-set primaries, is undoubtedly best adapted 

 to rapidity of motion. This will be most observable 

 in the Swallow, the Humming Bird, and the Night 

 Hawk, which of all birds are the most remarkable 

 for the nimbleness and agility of their movements. 

 How beautifully does the Swallow skim over the 

 meadows and lakes, or mount aloft in the air, now 

 wheeling to the one side and then darting like an 

 arrow to the other ! And how graceful are the antics 

 of the Night Hawk as he pitches his aerial summer- 

 sets, or gambols with matchless ease across the sky ! 



It will be observed that the wings of birds of rapid 

 flight are seldom very concave beneath ; on the con- 

 trary, they are generally quite flat when extended. 

 This flatness, although it contributes to the velocity 

 of motion as the bird sweeps along, destroys to a 

 great extent the power of direct ascent. Where the 

 wing is of moderate length and concave, as in the 

 Owl, and composed of loose soft feathers, the flight 

 is buoyant and noiseless, and quite different from that 

 of the Falcon, the feathers being too soft and yield- 

 ing to produce any whistling or rushing noise. A 



