, had spread widely over the great
northern continent, and had given rise to numerous varieties adapted to
special conditions of life. Among these some took to feeding on the
borders of clear streams, picking out such larvae and molluscs as they
could reach in shallow water. When food became scarce they would attempt
to pick them out of deeper and deeper water, and while doing this in
cold weather many would become frozen and starved. But any which
possessed denser and more hairy plumage than usual, which was able to
keep out the water, would survive; and thus a race would be formed which
would depend more and more on this kind of food. Then, following up the
frozen streams into the mountains, they would be able to live there
during the winter; and as such places afforded them much protection from
enemies and ample shelter for their nests and young, further adaptations
would occur, till the wonderful power of diving and flying under water
was acquired by a true land-bird.
That such habits might be acquired under stress of need is rendered
highly probable by the facts stated by the well-known American
naturalist, Dr.
Pages:
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220