184 
DIFFICULTIES ON THEOKY. 
Chap. VI 
and then proceeding to another, like a kestrel, and at 
other times standing stationary on the margin of water, 
and then dashing 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 often, 
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 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, on my theory, that such individuals would oc¬ 
casionally have given rise to new species, having anom¬ 
alous 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 
