STEERING 63 
have supple waists and poor steerers comparatively 
stiff ones, the Duck being a good deal the stiffest 
of those I have examined. 
It is difficult to account for the difference between 
the two Kestrels, but there is no doubt that the 
Duck is, of the birds in question, decidedly the 
stiffest. In fact these measurements make it a priori 
probable that suppleness of waist counts for 
a good deal. The result of the sideways bend 
must be that the bird is thrown on to its side—the 
attitude which is assumed when a sudden turn is 
to be made. 
For steering purposes, then, a bird has various 
methods at his disposal. He can take unequal 
wing-strokes or bend at the waist. Either of these 
means will put him in the attitude in which we 
see him steering to right or left, one wing pointing 
downward, the other upward. And he can use 
his tail as a rudder. Some birds may, no doubt, 
steer partly by means of their feet, but I doubt 
whether a foot is a very effective rudder. The 
Duck’s webbed feet do not seem to make him an 
adept at turning. 
