PHYSICAL FEATURES OF BIRDS. 267 



The Tail. 



The shape of the tail is in accord with the bird's 

 habits of flight and food-getting. Its main office is to 

 act as a rudder in flying, and as a balancer in alighting 

 from flight. The inter-action of the muscles of the 

 tarsus and the tibia with those of the toes is such that the 

 perchers among the birds are safe on the trees, even when 

 sound asleep. The natural bend of the bird's foot comes 

 between the heel and the toes. Now, with some of the 

 muscles attached to both tarsi and toes, and playing 

 around the bend of the foot, the toes are firmly locked 

 around the twig on which the bird may be sitting; and 

 the bird must make a real effort to let go rather than to 

 hold on. This coordination of muscular effort is perfected 

 only in the fully-developed bird; hence the young bird, 

 or the bird with its tail only partially grown, or the old 

 bird deprived of its tail, are both awkward in flight and 

 unsteady in alighting. 



Most birds walk on their toes with the heels con- 

 siderably elevated above the surface over which they are 

 walking. If you would see the force of this, try walking 

 on your toes with your heels elevated. The birds which 

 do walk on their heels, the cormorants and the grebes, 

 are exceedingly awkward and unskillful on the land. 



Long-tailed birds fly with greatest ease, and can 

 even turn sharp comers with marvelous success. A 

 robin, digging for a rapidly descending angleworm, uses 

 his tail as a sort of fulcrum for the necessary leverage in 

 raising the unlucky worm. All the tree-creeping birds 

 use the tail as a prop or brace. The motmot gesticulates 

 with its tail, as do also the angry wren, the robin when he 

 has his fighting blood up, the catbird when you go near 

 his nest, or the amatory blackbird when he is doing his 



