188 ORIGIN OF SPECIES 



ica, hovering over one spot and then proceeding to another, 

 like a kestrel, and at other times standing stationary on the 

 margin of water, and then dashing into it like a kingfisher 

 at a fish. In our own country the larger titmouse (Parus 

 major) may be seen climbing branches, almost like a creeper; 

 it sometimes, like a shrike, kills small birds by blows on the 

 head; and I have many times seen and heard it hammering 

 the seeds of the yew on a branch, and thus breaking them 

 like a nuthatch. In North America the black bear was seen 

 by Hearne swimming for hours with widely open mouth, thus 

 catching, almost like a whale, insects in the water. 



As we sometimes see individuals following habits different 

 from those proper to their species and to the other species of 

 the same genus, we might expect that such individuals would 

 occasionally give rise to new species, having anomalous 

 habits, and with their structure either slightly or considerably 

 modified from that of their type. And such instances occur 

 in nature. Can a more striking instance of adaptation be 

 given than that of a woodpecker for climbing trees and seiz- 

 ing 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. On 

 the plains of La Plata, where hardly a tree grows, there is a 

 woodpecker (Colaptes campestris) which has two toes before 

 and two behind, a long pointed tongue, pointed tail-feathers, 

 sufficiently stiff to support the bird in a vertical position on 

 a post, but not so stiff as in the typical w^oodpeckers, and a 

 straight strong beak. The beak, however, is not so straight 

 or so strong as in the typical woodpeckers, but it is strong 

 enough to bore into wood. Hence this Colaptes in all the 

 essential parts of its structure is a woodpecker. Even in 

 such trifling characters as the colouring, the harsh tone of 

 the voice, and undulatory flight, its close blood-relationship 

 to our common woodpecker is plainly declared; yet, as I can 

 assert, not only from my own observations, but from those 

 of the accurate Azara, in certain large districts it does not 

 climb trees, and it makes its nest in holes in banks ! In cer- 

 tain other districts, however, this same woodpecker, as Mr. 

 Hudson states, frequents trees, and bores holes in the trunk 

 for its nest. I may mention as another illustration of the 



