THE MACHINERY OF FLIGHT 89 
e.g. the Ducks. Mr. J. L. Bonhote has made a 
special study of the subject, and, quoting from him, 
I am able to give some very interesting and instruc- 
tive facts. The simultaneous moulting of the 
primaries occurs among the Divers, the Guillemots, 
the Razorbills, the Puffins, the Auks, and besides 
these among the Rails, e.g. the Moor-hens, the Land- 
rails, and the Crakes. Nearly all of them are water 
birds, and in the water they are fairly safe from 
their ordinary enemies. Some of them can dive, 
others can hide among reeds or under bushes; the 
Geese by force of numbers can, probably, beat off 
a bird of prey. A sea bird, if he is to moult in this 
fashion, must bea true diverin habit and in plumage, 
if not in name, and thus we find that the Cormorant 
(who is always wanting to dry his wings on a rock) 
and the Gannet moult gradually. When we turn to 
land birds the case of the Corncrake does not surprise 
us, for though he is a migrant, yet in his day-to-day 
life he trusts more to his legs than to his wings. 
The case of the Coot is perplexing ; unlike the Moor- 
hen, he is capable of flight throughout his moult ; 
but, as Mr. Bonhote points out, he is the only member 
of the Rail family that frequents estuaries and open 
sheets of water, and he is, in addition, an indifferent 
diver.* 
Legs. 
I have already pointed out how some birds use 
their legs in balancing and, possibly, for steering. 
Indirectly the great leg-power possessed by most 
birds is a most important aid to flight. In order to 
* See “‘ Eclipse Plumage and Flightlessness ” by J. L. Bonhote, 
in the Field, March 24, 1906. 
