248 THE STRUCTURE AND LIFE OF BIRDS cuwap, 
thing as an ache or cramp disturbs him. The wing- 
muscles are as unwearying as the leg-muscles that are 
stretched when he sits upon his perch. 
Steering. 
A modern writer boldly asserts that birds “ neither 
do nor can use their tails as rudders.” This shows 
how rash it is to dictate to nature what she may do 
or may not. I have already shown (p. 214) that the 
necessary muscles are present for moving the tail 
upward or downward, and for lowering one side 
relatively to the other. And a little observation with 
the naked eye, or, better, with a field-glass, will show 
that numbers of birds actually do pull down the left 
side of the tail when they wish to steer to the left, 
and wice versd. Rooks make great use of the tail in 
steering, the whole expanded fan of feathers being 
sloped so as to make quite a different angle with the 
horizon from that made by a line passing through 
the two wing-tips. In Jackdaws it is almost equally 
conspicuous. If, from below, you watch a Lark as he 
rises, you can easily see that he keeps his head to 
the wind by the perpetual play of his tail. The 
Swallow, House-martin, Sand-martin, and Swift guide 
themselves largely by the tail, as one might expect 
from its great development. The divided tail seems 
always to be much used as a rudder, though the loss 
of the single long feather from one side makes no ap- 
parent difference to a Swallow. Perhaps the domestic 
Pigeon shows tail-steering more conspicuously than 
any other bird ; he trusts much to it, and he is easy 
to observe. 
