17G TRANSITIONS Chap. VI. 



turc lead to clian^ed habits ; botli probably often occurring- al- 

 most sinuiltaneouslj. Of cases of champed habits it will sullice 

 merely to allude to that of the many British insects which now- 

 feed on exotic plants, or exclusively on artificial substances. 

 Of diversified habits innumerable instances could Ixi given : I 

 have often watched a tyrant flycatcher (Sauropha<^us sulphu- 

 ratus) in South America, hovering over one spot and then 

 proceeding to another, like a kestrel, and at other times stand- 

 ing 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 break- 

 ing them like a nuthatch. In North xVmerica 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 of a species following 

 habits widely different from those of their own species and of 

 the other species of the same genus, "we might expect that 

 such individuals Avould occasionally give rise to new sjiccies, 

 having anomalous habits, and with their structure either 

 slightly or considerably modified from that of their proper 

 type. And such*nstanc<?s do occur in Nature. Can a more 

 striking instance of adaptation be given than that of a wood- 

 pecker for climbing trees and seizing insects in the chinks of the 

 bark ? Yet in North America there are Avoodpcckci-s which 

 feed largely on fruit, and others with elongated wings which 

 chase insects on the wing. On the plains of La Plata, where 

 not a tree grows, there is a woodpecker (Colaptcs 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 woodpeckers, and a straight, strong beak. The beak, 

 however, is not so straight or so strong as in the typical wood- 

 peckers, but it is strong enough to bore into wood. Hence this 

 Colaptes in all the essential parts of its structure is a Avoodptxk- 

 er. Even in such trifling characters as the coloring, the harsh 

 tone of the voice, and inidulatory flight, all plainly dcclareil its 

 close blood-relationship to ouj common Avoodpecker ; yet, as I 

 can assert, not only from my own observation, but from that 

 of the accurate Azara, it never climbs a tree ! I may mention, 

 as another illustration of the varied haliits of the tril)C, that a 



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