The Bird Book 



is pointed ; that of the Owl is comparatively round. 

 With the pointed wing all the air must of necessity 

 escape backwards, and the maximum result is 

 gained from each beat. But a considerable por- 

 tion of air must escape at the end of a rounded 

 wing, and bring into being a force acting at right 

 angles to the line of flight, which has, of course, 

 an ill effect on speed. 



Another variation is apparent in many ocean 

 birds, such as the Albatross or our own Gannet, 

 which spend day after day upon the wing out of 

 sight of land. They even appear to sleep while 

 flying, and their wings are very long and compara- 

 tively narrow. Consequently a small movement 

 at the shoulder means considerable movement at 

 the tip. The wing is to all intents and purposes 

 a long lever, giving the bird all the advantages of 

 such a tool, and though the muscular exertion 

 needed is particularly tense while it lasts, it is 

 more than repaid by the results. 



We have all noticed the ease with which Sea- 

 gulls fly against the wind when it is blowing 

 half a gale. There appears little or no exertion, 

 the wings are not even fully extended, for the 

 pressure of the air on the wings obviates the 

 necessity for any except an occasional beat. 



One other bird we must mention in conclusion, 



which invariably uses whatever wind there is, for 



it performs the most difficult of all aerial feats. 



The Kestrel or Windhover has the power of 



lo 



