WIND AND FLIGHT 143 



they described their sedate spirals. A bird is cer- 

 tainly capable of a great deal during sleep. When 

 he sleeps standing on one leg, he is perpetually 

 making small adjustments in order to maintain his 

 balance. When a Duck sleeps floating on a pond 

 with one leg tucked up, he will keep the other 

 paddling, so that he may move in a circle and not be 

 driven by the wind into the bank, where a hungry 

 stoat may be waiting for him. But to sleep while 

 soaring is an altogether different matter. The 

 soaring bird has not only to make perpetual adjust- 

 ments, but also to feel the pulse of the wind, to be 

 alive to every gust and find out what adjustments 

 have to be made. But the fact that so good an 

 observer could hold this theory shows how sedate 

 the movement is. Though the pace may vary, there 

 is not a rapid sweep down a gentle incline in one-half 

 of a circle, then, in the other half, when the bird has 

 wheeled round, a slow advance with much gain 

 of altitude : nothing corresponding to the gallop of 

 the four-in-hand down the last fifty or hundred 

 yards of a hill, in order that the coach's momentum 

 may carry it some way up the hill that is immediately 

 in prospect. The circling is slow, sedate, and appar- 

 ently perfectly comfortable, and sometimes certainly 

 the bird keeps rising through a whole turn of the spiral. 

 He does not sweep downward in one part, then turn 

 and gain elevation. If all goes well, if the wind is all 

 that is required, there is no loss of altitude from 

 beginning to end of the turn ; there may be a gain 

 throughout. 



The birds that soar are all of considerable size 

 Small birds, however expert in flying, are, apparently, 



