The common Hawk Cuckoo of India (_Hierococcyx varius_) furnishes an example of this: “The brain-fever bird,” writes Finn, on page 58 of _Ornithological and Other Oddities_, “is the most wonderful feather copy of the Indian Sparrow-hawk or Shikra (_Astur badius_). All the markings in the hawk are reproduced in the cuckoo, which is also of about the same size, and of similar proportions in the matter of tail and wing; and both hawk and cuckoo having a first plumage quite different from the one they assume when adult, the resemblance extends to that too. Moreover, their flight is so much the same that unless one is near enough to see the beak, or can watch the bird settle and note the difference between the horizontal pose of the cuckoo and the erect bearing of the hawk, it is impossible to tell them apart on a casual view.” Moreover, the tail of the cuckoo sometimes hangs down vertically, thus intensifying the likeness to the hawk. It is quite possible that the brain-fever bird derives some benefit from the resemblance; indeed, it has been seen to alarm small birds, even as the hawk-like common cuckoo frightens its dupes, but, as D. Dewar pointed out, on page 105 of vol. 57 of the _Journal of the Society of Arts_, “this is not sufficient to explain a likeness which is so faithful as to extend to the marking of each individual feather. When a babbler espies a hawk-like bird, it does not wait to inspect each feather before fleeing in terror; hence all that is necessary to the cuckoo is that it should bear a general resemblance to the shikra. The fact that the likeness extends to minute details in feather marking, points to the fact that in each case identical causes have operated to produce this type of plumage.” This conclusion is still further strengthened by the fact that the likeness extends to the immature plumage, that is to say, exists at a time when it cannot assist the cuckoo in its parasitical work. Poulton meets this objection as follows: [Illustration: SHIKRA HAWK] [Illustration: HAWK-CUCKOO] Hypertely