^^"^ THE NEW EVOLUTION '^^^^ 



When well developed visual eyes occur they usually 

 are the chief reliance upon which the animal possess- 

 ing them depends for the discovery of its food, the 

 avoidance of its enemies, and the recognition of 

 its fellows. 



This is especially the case with birds which, taken 

 as a whole, have the most perfect vision of any group 

 of animals. No birds are blind, though forms which 

 invariably are blind occur in all the other groups of 

 vertebrates — the mammals, reptiles, amphibians and 

 fishes. It may be added that, together with extra- 

 ordinary sight, the birds also possess extraordinary 

 hearing. No birds are deaf. Smell, taste and touch, 

 however, are poorly developed in the birds. 



Birds might almost be described as wonderfully 

 efficient organic mechanisms activated and controlled 

 by light and sound waves to which they react with a 

 speed and an inflexible accuracy not seen in any other 

 creatures. 



The life-long powers of flight both by day and night 

 possessed by the great majority of birds, the extra- 

 ordinary development of sight and hearing, and the 

 correlated ability to seek out and find their food and 

 to detect and to escape from danger in unfamiliar 

 regions have made the birds, considered as a whole, 

 the most independent of their immediate surroundings 

 of any group of animals. Many different kinds of 

 birds are equally at home in far northern regions in 

 the summer and in the tropics in the winter. Such 

 an extensive economic range, involving great changes 

 in the immediate environment of the individuals, is 



