Page:Darwinism by Alfred Wallace 1889.djvu/246

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224
DARWINISM
CHAP.

will serve to illustrate this difference; which is frequently much greater and modified in an endless variety of ways (Fig. 22).

Numbers of species of pigeons, hawks, finches, warblers, ducks, and innumerable other birds possess this class of markings; and they correspond so exactly in general character with those of the mammalia, already described, that we cannot doubt they serve a similar purpose.[1]

FIG. 21.—Secondary quills.
FIG. 21.—Secondary quills.

Those birds which are inhabitants of tropical forests, and which need recognition marks that shall be at all times visible among the dense foliage, and not solely or chiefly during flight, have usually small but brilliant patches of colour

  1. The principle of colouring for recognition was, I believe, first stated in my article on "The Colours of Animals and Plants" in Macmillan's Magazine, and more fully in my volume on Tropical Nature. Subsequently Mrs. Barber gave a few examples under the head of "Indicative or Banner Colours," but she applied it to the distinctive colours of the males of birds, which I explain on another principle, though this may assist.