VII 



FLIGHT 249 



How, then, did the idea originate that the tail 

 was not employed as a rudder ? It was owing, I 

 believe, to the fact that a bird who has lost his tail 

 still manages to direct his course without great 

 difficulty. A Rook whom one of the many tussles 

 that go on in a rookery has left tailless is not a ship 

 without a helm. He can steer, but, as far as I have 

 observed, he cannot rest between the strokes of his 

 wings. The tail is a valuable parachute, and, bereft 

 of that, he must not loiter. His loss, too, reduces his 

 power of stopping suddenly. Moreover, steering is 

 not necessarily perfect steering, and I have no doubt 

 that a tailless swallow misses many gnats which he 

 might otherwise have caught. 



Two things are quite clear, then: (1) the tail is 

 a rudder ; (2) there is some other means of steering. 

 I think I have seen gulls when flying fast adopt 

 another method which is in its nature the same- 

 let down a foot on the side towards which they wish 

 to go. More often they kick vigorously when they 

 make a sudden turn, or when they are about to settle, 

 working the feet together, and not alternately as they 

 do in swimming. Clearly, steering by means of the 

 feet must be limited to web-footed birds. 



There is another plan very different from those we 

 have mentioned. If he wishes to steer to the left, the 

 bird flings himself on his left side, his left wing point- 

 ing downward and his right upward. The onward 

 course of the fore part of his body is retarded by his 

 outspread wings, the hinder part moves more quickly, 

 and this causes him to describe a curve. So far, it is 

 simple enough, but when we come to inquire how the 



