THE NORTH AMERICAN FAUNA 177 



We might also include in this category the snowy heron, the roseate 

 spoonbill and other birds that have been slaughtered for their plumage. 

 Although the economic value is here the direct motive for the slaughter, 

 this value grows out of unusual (and beautiful) modification of the 

 plumage. 



The preceding paragraphs are necessarily sketchy, because the sub- 

 ject is too large to treat in detail and it is now desirable to gather up 

 the threads. 



Briefly, the general tendency of the North American fauna is toward 

 mediocrity. Large species are giving way to small; bizarre species to 

 commonplace. Marsh-loving and forest-loving animals disappear with 

 the advance of civilization, and grass-loving species that are able to exist 

 in fence rows and pastures survive. Animals that yield products of 

 value vanish before the hand of man ; likewise his enemies are destroyed 

 unless protected by small size and great fecundity. Courage and the 

 social instinct are at a discount and cunning and timidity at a premium. 



Finally man is beginning (and only beginning) to shape the destiny 

 of his God-given dominion "over the beasts of the field and the fowls 

 of the air." To make this dominion an intelligent reality is the aim of 

 present-day biological science. 



