166 ON THE ORIGIN OF SPECIES 



occasionally have given rise to new species, having 

 anomalous habits, and with their structure either 

 slightly or considerably modified from that of their 

 proper type. And such instances do occur in nature. 

 Can a more striking instance of adaptation be given 

 than that of a woodpecker for climbing trees and for 

 seizing insects in the chinks of the bark ? Yet in North 

 America there are woodpeckers which feed largely on 

 fruit, and others with elongated wings which chase 

 insects on the wing ; and on the plains of La Plata, 

 where not a tree grows, there is a woodpecker, which 

 in every essential part of its organisation, even in its 

 colouring, in the harsh tone of its voice, and undulatory 

 flight, told me plainly of its close blood-relationship 

 to our common species ; yet it is a woodpecker which 

 never climbs a tree ! 



Petrels are the most aerial and oceanic of birds, yet 

 in the quiet Sounds of Tierra del Fuego, the Puffinuria 

 berardi, in its general habits, in its astonishing power 

 of diving, its manner of swimming, and of flying when 

 unwillingly it takes flight, would be mistaken by any 

 one for an auk or grebe ; nevertheless, it is essentially 

 a petrel, but with many parts of its organisation pro- 

 foundly modified. On the other hand, the acutest 

 observer by examining the dead body of the water-ouzel 

 would never have suspected its sub-aquatic habits ; yet 

 this anomalous member of the strictly terrestrial thrush 

 family wholly subsists by diving, — grasping the stones 

 with its feet and using its wings under water. 



He who believes that each being has been created as 

 we now see it, must occasionally have felt surprise 

 when he has met with an animal having habits and 

 structure not at all in agreement. What can be 

 plainer than that the webbed feet of ducks and geese 

 are formed for swimming ? yet there are upland geese 

 with webbed feet which rarely or never go near the 

 water ; and no one except Audubon has seen the 

 frigate-bird, which has all its four toes webbed, alight 

 on the surface of the sea. On the other hand grebes 

 and coots are eminently aquatic, although their toes 



