Locomotion in Young Birds. 79 



no matter how deeply the congenital ability to fly is 

 founded in heredity. 



Individual differences in the manner of flight are partly 

 congenital as particularized modes of activity, partly 

 enforced by congenital differences of structure. When, for 

 example, a falcon is flown at a heron overhead, the quarry, 

 as soon as he sees the hawk, flies upwards, the falcon 

 following. The difference in mode of flight is then well seen. 

 The heron, with his large concave blunt wings and light 

 body, rises in narrow circles. The hawk, with her long 

 pointed wings and relatively heavy body, sweeps through a 

 wide spiral, more than making up for the greater distance 

 she has to cover by her rapidity of flight. This continues 

 until the falcon has gained sufficient advantage to enable 

 her to stoop at the quarry. 



The different modes of flight in correlation with different 

 types of wing ; the problems connected with soaring and 

 sailing flight ; these are tempting themes. But they are 

 beyond our present purpose, and I have nothing new to 

 say on them. That the bird of skilled flight is able to feel 

 in some way the strength and varying direction of the air- 

 currents seems beyond question. Is it the pressure on the 

 feathers of the breast that affords the necessary data which 

 j the bird utilizes in the acquisition of that experience which 

 through much practise makes flight perfect ? We do not 

 know. We can only say that the experience, however 

 gained, is a factor in that acquired power which is founded 

 i on a congenital basis due to hereditary transmission. 



