24S THE STRUCTURE AND LIFE OF BIRDS chap. 



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 vice versa. 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. 



