POSITIONS ASSUMED BY BIRDS IN FLIGHT. 199 



appears pushed up and supported by them ; and this is 

 precisely its position. The wings in their rapid descent 

 found resistance in the air, and as soon as this resistance 

 exceeded the force of gravity acting on the bird, the body 

 was elevated at the same time that it was driven forward, 

 only, of course, to sink once again on the wings being 

 raised. Thus the path of a flying bird is a succession of 

 ups and downs, but the movements of the wings being 

 so very much greater in extent cloak those of the body, 



and so gracefully 

 and smoothly are 

 the actions per- 

 formed that we do 

 not realize the un- 

 dulatory nature of 

 the course. 



The attitude of 

 the right-hand top 

 bird, a Kittiwake, 

 in the same photo- 

 graph (Figure 1), is 

 interesting, as it 

 shows the bird 

 steering by the 

 aid of its feet. 

 The very extensive 

 use some birds 

 make of their 

 feet during flight 

 requires consideration. Not only are they freely used for 

 steering, but they are also often employed as brakes to 

 lessen speed, much in the same way as a drag is used 

 to take way off an incoming vessel. In Figure 2 the 

 immature Gannet there depicted is trailing its partly 

 expanded and lowered feet, thereby causing considerable 

 resistance to its forward progress. To birds which quarter 

 the surface of the ocean for a livelihood, feet have yet 

 another use during flight. As the bird swoops downwards 



FIGURE 2. — THE FEET USED AS BRAKES 

 {Photographed by Bentley Beetham.) 



