In all her products, Nature only develops her simplest germs. One would say that it was no great stretch of invention to create birds. The hawk which now takes his flight over the top of the wood was at first, perchance, only a leaf which fluttered in its aisles. From rustling leaves she came in the course of ages to the loftier flight and clear carol of the bird.

A Week on the Concord and Merrimack Rivers (ed. 1873)