Page:Popular Science Monthly Volume 75.djvu/568

562 Among the genera that move erect without crouching in the vicinity of their prey, and catch it upon surfaces below their level, and which are commonly effaced as to their top contours, by white in their costume, are herons, cranes, pelicans and the omnivorous swans, geese and ducks. And a similar use of white effaces the rear view of an immense number of widely separated members of the animal kingdom which tend to be seen by their pursuers against the sky. Among these are hares, deer and antelopes, ground-nesting birds that commonly spring on wing from the nest on being flushed, such as waders, ducks and geese, many passerines, and such hawks as nest on the ground. These all wear some white rump or tail pattern, which obliterates them in the most magical way, against the sky, exactly while, in getting under way, they are for a fateful instant within springing reach of the cougar, lynx or fox that, with head close to the ground, has crept up to them. White patterns abound on aerial passerines in general, but even white wing bars are lacking from such as keep so close to the ground that no enemy sees them against the sky. And among small rodents none has top-white unless, like the jerboa, he jumps high enough to be seen by his pursuer against the sky.

Now, while these white top patterns seem to be universally employed wherever they can be of the above service, on the other hand, they are conspicuously lacking from the rears of such ground-nesters as habitually run, instead of flying from the nest, and thereby avoid showing against the sky, to terrestrial eyes. Such are gallinaceous birds, tinamou, rails and many other sedge-haunting species. (Gallinules whose upturned tails present, as they fly, a white sky-picture, probably keep their tails down when they slink from their nest.)

The white patterns on the breasts of several kinds of bear, which Mr. Pocock has classed as warning colors, serve perfectly the same obliterative purpose that we find in all the rest of upward-facing white patterns. (These patterns face upward when the bear stands erect, i. e., face upward to the degree necessary for catching top light.) Now, we find that for recognition a monochrome silhouette, especially in a thicket, is far superior to a patterned one (see Fig. 8), and also we have small grounds for thinking that such bears, when standing erect in the jungle, have need to be afraid of being attacked by mistake by any of their neighbors that would avoid them if they recognized them. On the other hand, be the beards object, in thus assuming man's attitude, either aggression or defense, he gets the same general advantage out of escaping detection, and the chance of enjoying this boon is, as we now realize, greatly increased by the chance of this light patch being, at the right moment, just sufficiently illuminated to pass for a sky-hole through the dark mass of shrubbery of which the erect bear forms the dark center. All woodsmen know that when one has followed with the eye some bird