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adapted for a particular mode of existence, which shows 

 that birds are racially specialized. 



Birds are unusual when compared with other vertebrates 

 in having the ability to fly. Their exceptional agility has 

 made it easy for them to capture food and escape from 

 enemies, but they are not on the whole as versatile as 

 mammals, partly because they are too specialized. They 

 depend largely upon quickness and the acuteness o? their 

 sense organs. This has led to the extreme development of 

 those parts of the nervous system which correlate accurate 

 muscular movements and control reflexes; but the parts 

 which have to do with thinking and scheming are com- 

 paratively simple. In the brain of a bird the cerebellum 

 (which is concerned largely with the coordination of 

 muscular activities) is very large and the cerebral lobes 

 (where higher mental qualities reside) are small. In a 

 mammal both regions are well developed. Birds, then, 

 as a race, have sacrificed their power to develop great 

 mental ability, probably because they became able to fly 

 early in their evolution, and then were so specialized that 

 they could not branch off on new evolutionary lines. The 

 toes on the front limbs became degenerate to allow the 

 formation of more effective organs for flight; the neck 

 grew long and flexible to compensate for the resulting handi- 

 cap in securing food; the teeth gave place to a horny beak. 

 Specialization along such lines for a time made birds so 

 successful that they became modified structurally to such 

 an extent that they can never be racially youthful and 

 have broad possibilities again. Birds as a race are in their 

 old age. 



As long as birds succeed' with their present adaptations, 

 however, they will dominate the air, and must be given 

 credit for their exceptional flying ability. A fish-hawk 

 can move as fast as an express train and may feed at will 

 from the ocean or an inland lake, on the top of a mountain 

 or in the bottom of a canyon. The best flyers among 

 birds are the long-winged gulls, vultures, hawks, and man- 



