CHAPTEK 11. 



THE LIVING BIRD. 



Factors of Evolution. — If while in the fields we ob- 

 serve birds with an appreciative eye, we shall soon be 

 impressed with the great diversity shown in their struc- 

 ture and habits. The Fish Hawk plunges from the air 

 into the water and grasps its prey with merciless talons. 

 The Hummingbird daintily probes a flower. The Wood- 

 pecker climbs an upright trunk, props itself with its 

 stiff, pointed tail-feathers, while with its chisel-shaped 

 bill it excavates a grub and then impales it with its 

 spearlike tongue. These birds tell us a wonderful story 





Fig. 2.— End of spearlike tongue of Pileated Woodpecker. (Much enlarged.) 



of adaptation to the conditions of life, and, knowing that 

 they have descended from a common ancestor, we ask, 

 " Why do they now differ so widely from one another ? " 

 Biologists the world over are trying to satisfactorily 

 answer this question, and it is impossible for me to 

 even mention here all the theories which they have 

 advanced. However, some knowledge of the most im- 

 portant ones is essential if you would study the relation 

 between the bird and its haunts and habits. The Dar- 

 win-AYallace theory of Natural Selection, in more or less 



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