88 THE FLIGHT OF BIRDS. 
From whatever point of view we look at it, a flight- 
feather is a wonderfu™@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 
(sce Pl. vu, 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 all, 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, 
