100 THE FLIGHT OF BIRDS 
it is possible for them t@gwim, and the smallest with 
which it is possible for them to fly. The wing-beats 
during flight are marvellously rapid ; there is visible 
a rapidly-moving body and a blur on either side 
where the wings are working with terrific speed. 
The Water-Ouzel searches for his food among the 
weeds in the bed of fast-running streams, and he, 
too, has short wings that he plies with very great 
rapidity. 
The rolling flight of Partridges and Grouse is very 
striking. When you put them up, they never, till 
they have got some distance off, keep on an even 
keel. Probably this rolling flight makes it less easy 
for big birds of prey to swoop down upon them with 
true aim, and it may help them to glance at a 
pursuing enemy. In fact, the Partridge and the 
Grouse are still, in their habits, adapting themselves 
to an environment of raptorial birds rather than to 
an environment of sportsmen and gamekeepers. 
The zigzagging flight of the Snipe—a very spirited 
and characteristic performance—is a different thing ; 
the line of flight is a zigzag, but at the same time 
there is the rolling that we see in the Grouse’s flight. 
It is well calculated to confuse the aim of an assailant, 
whether he be a bird of prey or a novice with a gun. 
The way in which the long-necked and the long- 
legged birds carry their necks and their legs is inter- 
esting. The Duck and the Goose stretch their necks 
forward to their full length. This may be because 
the breastbone that carries the heavy flight-muscles 
is very long, so that the head and neck are used to 
balance the weight farther back. The Heron flies 
habitually with his neck bent—a remarkable fact 
