CLEANING-UP TIME 285 



The numbers of our resident chaffinches, green- 

 finches, and sparrows no more increase than those 

 of the nightingale, whitethroat, cuckoo that must 

 brave two long flights across the sea. Their 

 flocks have now been so cleaned up that every 

 bird of them seems to be a perfect specimen. He 

 is glossy with health, and brightly painted with 

 the totems of his order. There is no laggard 

 when the school moves on to new feeding ground, 

 no novice bird waits on more experienced ones 

 in order to beg a crumb. Every bird knows all 

 the rules of the game, and it is just a matter of 

 chance which of the troupe makes the next dis- 

 covery of food. Yet even now there are more 

 birds than Nature requires as an annual stock, 

 and these armies of perfect units must be still 

 more perfected by the removal of some more of the 

 least unfit. No human eye could tell which are 

 the doomed ones, but the measuring rod of 

 Natural Selection is one of infinite discrimination. 



