Page:Auk Volume 13-1896.djvu/164

﻿ objects manifest themselves to the eye, is effaced at every point, the cancellation being as complete at one point as another, as in Fig. C of the diagram, and the spectator seems to see right through the space really occupied by an opaque animal.

Fig. 1 of a Ruffed Grouse shows this arrangement of color and light. This bird belongs to the class in which the arrangement is found in its simplest form, the color making a complete gradation from brown above to silvery white beneath, and conforming to every slightest modelling; for instance, it grows light under the shelving eyebrow, and darker again on the projecting cheek.

When he stands alive on the ground, as in Fig. 2, his obliteration by the effect of the top light is obvious.

Writers say "he is so nearly like the color of his surroundings that you cannot see him." Fig. 3 is to show that they ascribe the concealment to the wrong cause. I merely took the bird shown in Fig. 2, and accurately tinted his under parts with brown to match his back, and in less degree tinted his sides, till I had reduced him to uniformity of color all over; but I did not, of course, change his upper surfaces at all. In short, I extended his 'protective' colors all over him.

Now observe the effect on replacing him in a life-like position. He is completely unmasked. The reader has but to compare the distance at which he can distinguish a bird in No. 2 and in No. 3 respectively, to see whether simple 'protective coloration,' as ordinarily defined, is the true cause of this concealment, or whether this compound gradation of color and light is the true cause.

Fig. 4 and Fig. 5 show that his colors are powerless to conceal him in any position except the upright one which he holds when alive, and Figs. 6 and 7 do the same for the Woodcock.

In Figs. 5 and 6, notwithstanding the fact that we have even the strongest 'protective' colors towards us, the bird is by no means concealed.

The Woodcock series corresponds to that of the Ruffed Grouse. Fig. 8 shows a female on her nest, very difficult to find. In Fig. 9 the bird has been treated exactly as I treated the Ruffed Grouse in Fig. 3. Observe that she is essentially more conspicuous, though not a feather of her upper parts has been artificially painted.