There is an interesting point to notice about the woodpeckers. This reversed fourth toe is curiously variable in length. In the flickers, with its claw, it is a little shorter than the middle (third) toe with its claw; in the red-heads and their friends it a little exceeds the middle toe and claw; in the downy and the hairy it is much the longest toe, and in the ivory-billed woodpecker it is abnormally developed. We at once judge that it is some indication of the bird's manner of life, and we look for it to be largest in the species that live continually upon the trunks of trees, obtaining most of their food by drilling. We expect to see the finest development of drilling bill accompany this enormously developed toe, and we find them both in the ivory-billed woodpecker. In imagination we clearly see the use of it. The great bird, keen in his quest of grubs, sidling hastily round the tree, in an unsteady balance and unsupported by his tail, throws one long hind toe downward to steady himself, hooks the other into the bark above him, and hangs between the two as firmly supported as in his ordinary position. No doubt he does do this, but does it prove the supposition that the heaviest and most arboreal woodpeckers have the greatest development of the fourth toe? Not at all. There is our rare acquaintance the logcock, or pileated woodpecker, a bird nearly as large as the ivory-billed, one of the most persistent of our tree-climbers and more than any other woodpecker I ever observed given to scratching rapidly round and round a tree-trunk, clinging at ease in almost any position except head-downward, and drilling incessantly and at all seasons for grubs; he is a typical woodpecker of the largest size, but his hind toe and claw are, if anything, a trifle shorter than his middle toe with its claw. He throws it out and uses it as we have described, but it has not that disproportion to the other toes which we expected to find as the result of a strictly arboreal life.
What have we proved? We have not shown that the long toe is _not_ more useful than the shorter one,--that is a matter of observation; but we have failed entirely to show that it is so, and this can be done only in one of two ways: either by proving that the logcock's habits are not what all previous observers have believed them to be,--which would be assuming a great burden of proof; or by demonstrating that his ancestry explains why his feet do not illustrate our theory,--and this, though it is undoubtedly the true solution, could be settled only by a very learned man.