Ways of Nature by John Burroughs — Read

To what lengths the protective resemblance theory is pushed by some of its expounders! Thus, in the neighborhood of Rio Janeiro there are two species of hawks that closely resemble each other, but one eats only insects and the other eats birds. Mr. Wallace thinks that the bird-eater mimics the insect-eater, so as to deceive the birds, which are not afraid of the latter. But if the two hawks look alike, would not the birds come to regard them both as bird-eaters, since one of them does eat birds? Would they not at once identify the harmless one with their real enemy and thus fear them both alike? If the latter were newcomers and vastly in the minority, then the ruse might work for a while. But if there were ten harmless hawks around to one dangerous one, the former would quickly suffer from the character of the latter in the estimation of the birds. Birds are instinctively afraid of all hawk kind.

Wallace thinks it may be an advantage to cuckoos, a rather feeble class of birds, to resemble the hawks, but this seems to me far-fetched. True it is, if the sheep could imitate the wolf, its enemies might keep clear of it. Why, then, has not this resemblance been brought about? Our cuckoo is a feeble and defenseless bird also, but it bears no resemblance to the hawk. The same can be said of scores of other birds.