88 THE FLIGHT OF BIRDS 



From whatever point of view we look at it, a flight- 

 feather is a wonderful thing. It provides a large 

 expanse to support the bird's weight, it is elastic, 

 it is light and at the same time strong. Moreover, 

 it is renewed every year, and in such a way that the 

 bird does not even for a day lose his power of flight. 



Moulting. 



A living machine differs from a man-made machine 

 in many ways, and notably in this, that it has as an 

 indispensable characteristic, the power of self -repair. 

 When a bird's feathers are broken or worn out, they 

 must somehow be replaced. Now nearly all birds 

 that fly shed their flight-feathers gradually and in 

 pairs, so that, though during the moult they are not 

 at their best, yet they can always rise on the wing 

 (see PI. vni, 4). The Goose has somehow earned 

 a widespread reputation for stupidity, but the most 

 stupid thing that he does is not, I believe, generally 

 known. He moults so rapidly that for a time he 

 is reduced to helplessness. In the island of Kolguev, 

 the Samoyeds drive thousands of moulting geese, 

 who can only swim or run, into great nets and thus 

 provide themselves with a store of food for the Arctic 

 winter. 



But, after aJl, this rapid method of moulting would 

 involve but little danger for the Goose if man had 

 not arrived on the scene, since his way of life became 

 stereotyped. Many birds, not geese alone, have 

 failed to find any means of escape from their enemy 

 with his ever-changing method of attack. There 

 are other birds which shed all the primary-feathers 

 simultaneously without any disastrous consequences, 



