FOOT OF BIRDS. 



291 



Head and Leg of the Ibis. 



to fly, would otherwise have been left without defence against 

 the more powerful beasts of prey they are extremely robust and 

 muscular, so as to enable these colossal birds to scour the sandy 

 plains with such velocity, that their feet scarcely appear to touch 

 the ground. 



In the waders, who are also most excellent runners, they are 

 not so strongly built, but 

 their uncommon length 

 is extremely well-suited 

 for walking on swampy 

 ground, or for fording 

 shallow estuaries and 

 marshes. A greater mus- 

 cular strength would have 

 been superfluous, as the 

 body they have to carry is 

 proportionably small and 

 light, and, besides, a more 

 robust construction could only have been obtained by a greater 

 weight, which would have been a serious inconvenience to birds 

 which pass so great a part of their lives on a treacherous and 

 unstable soil. 



Planted in the centre of the body, they are thus enabled to 

 carry its equally-distributed weight with the least possible 

 amount of exertion ; and as they are only feathered as far as the 

 middle of the thigh, they are the better enabled to wade deep 

 into the water, particularly as their straight and elongated toes, 

 which are also frequently lobed or webbed, prevent them from 

 sinking too deeply into the mud. 



A most remarkable example of the provident care with which 

 the formation of the toes of the waders has in every case been adap- 

 ted to the peculiar circumstances of their life, is afforded us by the 

 yacana, in which they are distinguished by extraordinary length, 

 and armed, moreover, with equally long spinelike claws, espe- 

 cially that of the hinder toe. For a bird destined to pace the 

 ground, toes such as these would have beeD as inconvenient as the 

 snow-shoes of a Laplander ; but to the Tacana they are extremely 

 serviceable, as from the wide surface over which they extend, they 

 enable this extremely light bird to pursue its food, consisting of 



u 2 



