FOOD AND FEEDING 97 



the pheasants, wherein the leg is armed with formidable spurs. 

 In the cassowary the claw of the inner toe is of enormous size, 

 and this is used as a weapon of offence. 



Some birds, on the other hand, have the wing armed with 

 spurs, as in the spur-winged plovers and spur-winged goose ; 

 or large, bony knobs may take the place of spurs, as in swans, 

 and the extinct solitaire, a gigantic fossil pigeon. These weapons 

 are used by the males in fighting rivals. 



How nicely the balance of Nature is adjusted, how exactly 

 the various organs of the body reflect the uses to which they 

 are put, increasing as required, in size or strength, or on the 

 other hand decreasing as the need therefor grows less, is well 

 reflected in the relative length of the legs in the frigate bird- 

 one of the gannet tribe and in the stilt one of the plover 

 tribe. 



The frigate bird passes the greater part of its life on the 

 wing, and consequently has no use for legs save as supports while 

 resting. As a consequence these legs have dwindled in size till 

 little more than the feet remain ; while the wings have increased 

 enormously. In the stilt the wings are only of moderate size, 

 while the legs, which are used for wading in deep water in search 

 of food, are of prodigious length. The different forms of the 

 beak and feet (pp. 92 and 95) illustrate this lesson no less 

 clearly. 



But the wings are no less instructive in this connection, and the 

 attention of children may profitably be drawn to, say, the long, 

 pointed wings of the swift, and the short rounded wings of the 

 wren. The former is a bird which obtains its food entirely while 

 on the wing and rarely alights upon the ground, while the latter is 

 a bird which seldom flies, and never far, save when on migration. 

 Swifts which happen to be born with wings below the standard 

 die from lack of ability to obtain food. Flight being unnecessary 

 to the wren, there is no demand for large wings. 



VOL i. 7 



