EFFECT UPON HEALTH OF MAN 57 



damage has been done to the cotton- and corn-fields 

 of Alabama and Mississippi by the crustaceans. 



As Scavengers 



Perhaps the most important minor relation of 

 birds to mankind is their work as scavengers. 

 Although many species function in this way, the 

 best known group is the vultures. 



So great has been the need in nature of a street- 

 cleaning department that two separate kinds of 

 vultures have arisen. The vultures of the New 

 World are quite different in anatomical structure 

 from those of the Old World. They have evolved 

 along parallel lines ; that is all. The external ap- 

 pearance is virtually the same, their habits are 

 similar, and their functions are identical, but the 

 birds are not closely related. They come from 

 two different stems of the hawk family. 



In most tropical cities the streets are ten- 

 anted by great numbers of vultures who " po- 

 lice " the gutters of garbage which, if left to lie 

 there, would soon pollute the entire neighbor- 

 hood. The meat-markets are infested by them, 

 and they greedily swallow all discarded scraps of 

 meat. So active is the efficiency of the " turkey- 

 buzzards " in our own Southern States that, ex- 

 cept in the cities and large towns, dead animals 

 are seldom buried. The bodies are dragged to 



