142 THE FLIGHT OF BIRDS 



with his wings. He gets the wind to lift him, and 

 as he rises he circles, or, more correctly, describes 

 a spiral or helix. It is a marvellous performance. 

 Had we not an unlimited capacity for getting used 

 to anything, we should be lost in wonder whenever 

 we see this splendid achievement. 



Many of the larger birds are proficient at it — 

 Eagles, Vultures, Pelicans, Storks, Falcons, Kites, 

 Buzzards, Ravens, Gulls and others, all, even the 

 smallest of them, possessed of wings that have a 

 very considerable area, and are very different in 

 outline from the long, narrow wings of the Tern or 

 the Swift. The Gull's wing is less definitely a soaring 

 wing than the others mentioned ; adapted both for 

 soaring and long-distance flapping flight, it is a 

 compromise between the broad and the narrow.* 



Evidently breadth, and not only length, is im- 

 portant in soaring, and the great primary feathers 

 spread out, leaving very noticeable gaps between 

 them. Probably this gives steadiness, preventing 

 a too sudden escape of air from under one wing. If 

 a bird is watched through a field-glass or telescope, 

 the upward bending of these great feathers by the 

 force of the wind is sometimes quite noticeable, the 

 first primary being often bent considerably more 

 than the others (see the Frontispiece). 



It is a slow, sedate movement, this circling high in 

 air. Mr. S. E. Peal,f who used to gaze with wonder 

 at the circling of the Adjutants, a kind of Stork noted 

 for their soaring, over the plain of Upper Assam, 

 held, if I remember rightly, that the birds slept as 



* See PI. xiv. 



f See Nature, Nov. 4, 1880 ; Sept. 26, 1889 ; May 21, 1891. 



