LEGS 27 



ostrich can run more rapidly than the horse, the barn fowls 

 can walk and run, the bluebird can only leap or hop, while the 

 auks can scarcely waddle. 



The legs, like the bills, show a wonderful variety of modifi- 

 cation in the different groups of birds. A careful study of 

 either or both these parts will enable one to place any bird 

 into its proper family. The use of the legs as a means of 

 classification makes this chapter an important one, and it 

 should be thoroughly studied before any attempt is made to 

 determine the names of birds by the aid of the Key. 



Parts. — The terms applied to the different parts of the legs 

 of birds will be better understood by the student if he recalls 

 what he learned in physiology about the bones of his own leg, 

 and then compares the joints with those in the legs of a bird. 

 In the sparrows and a large proportion of other birds, the space 

 from the heel to the claws is all that shows of the leg (see 

 cuts, pp. 15 and 22) ; these parts are called tarsus and toes. 

 The tibia is entirely hidden by the feathers, and the thigh is so 

 united with the skin of the body as to seem a part of it. In 

 the grebes even the tibia is confined by the skin of the body. 



The joint which bends forward in the hind limbs of all ver- 

 tebrate animals is the knee, and the joint which bends back- 

 ward is the heel. An examination of the horse's hind leg will 

 show that it also has its heel as near the upper as the lower 

 end of what appears to the eye as the leg, and that the knee is 

 fastened to the body by the skin. 



Covering of legs. — The thigh is feathered in all birds. The 

 tibia is also feathered in most of the higher birds ; but among 

 wading birds there are on the tibia all stages of covering, from 

 a completely feathered covering in the woodcock to one almost 

 completely scaly in the stilts. The tarsus in most birds is 

 scaly, but the grouse have it more or less completely feathered. 

 Most of the owls have the tarsus fully feathered, and many 

 of them the toes also. The barnyard fowls often have curious 

 tufts of feathers on otherwise bare sections ; some of the wild 

 birds also have some odd tufts irregularly placed. 



