HOW THE BIRDS KNOW 337 



stinct," "subconscious mind," or covered by the 

 simple statement that the birds know matters little. 

 In an effort to learn exactly what the birds know 

 in order to protect them and educate ourselves, 

 great care should be used to keep the head level 

 and leave the heart out of the question. The proc- 

 esses of nature are distinctly cold-blooded. Every- 

 where the strong preys upon the weak. Poetic 

 interpretation and romancing make beautiful read- 

 ing, but bad natural history. Some things which 

 birds do are done for such obvious reasons that 

 anyone can understand them, some we can only 

 surmise, and concerning some we can not make a 

 plausible surmise. It is reasonable to suppose 

 that birds eat the food they do because when 

 nestlings they were fed those things. Why birds 

 of the same size, of closely related species, living 

 in the same places and having access to the same 

 foods, are taught some to eat grasshoppers, some 

 worms, and some seeds, is a mystery. If they had 

 the same food to eat, they still would remain dif- 

 ferent. You remember that grass from the same 

 meadow makes feathers on a goose, wool on a sheep, 

 bristles on a pig, and hair on a horse; and the same 

 grass gives different form and feathering to the 

 goose and the duck, eating it side by side. Certain 

 birds, having accomplished their evolution on cer- 

 tain kinds of food, have gone on eating them un- 

 til their structure unfits them for anything else. 

 The seed-eaters have evolved heavy, short, sharp 



