86 THE COMING OF THE BIRDS 



As to the beginning of the care of the eggs, we 

 have, naturally, no positive knowledge whatever. 

 Nesting is very varied in nature to-day, and is in 

 some cases extremely simple. I would venture to 

 conjecture that for millions of years — possibly until 

 the last Ice Age — birds did not nest at all. But they 

 must have begun early to brood over the eggs. If 

 the mother needed feathers to keep her warm, the 

 eggs needed warmth to hatch. Here again there is 

 not a quite sudden leap from the reptile world. Some 

 of our living reptiles bury their eggs in a sort of 

 "nest." 



These are merely general and superficial considera- 

 tions. I am only sketching the broad lines of develop- 

 ment. It is not possible or desirable here to go more 

 deeply into the matter. Special authorities on birds 

 must be consulted. I merely wish to make the bird 

 world broadly intelligible. Even children to-day 

 ought to know more than that there are birds because 

 there is air, and fishes because there is water, and 

 beasts because there is land. The doctrine of evolu- 

 tion, which throws such a wonderful light on nature, 

 is shockingly neglected in our schools. ** Nature 

 study " is a poor thing without evolution. 



There are birds because once upon a time the earth 

 was for two or three hundred thousand years in the 

 grip of an Ice Age, and in some regions all the higher 

 animals (reptiles) would have perished if they had 

 not developed the "heating-apparatus" of the bird. 



