Colouring of the Cuckow's Egg

Abstract

As I see Professor Newton has, in his very interesting paper on Dr. Baldamus' theory of the colour of Cuckoo's eggs, noticed my “stigmatising” the Doctor's theory as “wild”, in my “Birds of Somerset”, will you be kind enough to allow me space for a few lines on the subject? Although it is with great diffidence that I venture to differ from Professor Newton, I still cannot help considering Dr. Baidamus' theory as “wild”, not perhaps as it appears under the manipulation of Professor Newton, for he seems to me to have pruned and pared it down so nicely that there is but little of the original left; and I think he would not much differ from me in my opinion as to the wildness of the theory, if he had to accept all the allegations in Dr. Baldamus' paper published in Naumannia.* For instance, compare the following passage in Professor Newton's paper in No. III. of NATURE with some passages from Dr. Baldamus' paper:— “Having said thus much, and believing as I do the Doctor to be partly justified in the carefully-worded enunciation of what he calls ‘a law of nature,’ I must now declare that it is only ‘approximately,’ and by no means universally true, that the Cuckow's egg is coloured like those of the victims of her imposition. Increase as we may by renewed observations the number of cases which bear in favour of his theory, yet, as almost every bird's-nesting boy knows, the instances in which we cannot, even by dint of straining our fancy, see resemblances where none exist, are still so numerous as to preclude me from believing in the generality of the practice imputed to the Cuckow. In proof of this I have only to mention the many eggs of that bird which are yearly found in nests of the Hedge-Sparrow in this country, without ever bearing the faintest similarity to its well-known green-blue eggs. One may grant that an ordinary English Cuckow's egg will pass well enough, in the eyes of the dupe, for that of a Titlark, a Pied Wagtail, or a Reed Wren, which according to my experience are the most common foster-parents of the Cuckow in this country; and indeed one may say, perhaps, that such an egg is a compromise between the three, or a resultant, perhaps, of the three opposing forces; but any likeness between the Hedge-Sparrow's egg and the Cuckow's so often found alongside of it, or in its place, is not to be traced by the most fertile imagination. We must keep, therefore, strictly to the letter of the law laid down by Dr. Baldamus, and the practice imputed to the Cuckow is not universally, but only approximately true.” This certainly is very different from Dr. Baldamus' own statement:— “If Mr. Braune, the forester of Griezland, had not cut this large Willow Wren's (Shippolais) egg (as it seems) out of the ovary of the Cuckoo, which was killed as she was flying out of the Willow Wren's nest; if Count Rödern, of Breslau, was not a reliable authority that this apparent Redstart's egg was taken out of the nest of the Redstart (Ruticilla phœnicurus); if M. Halricht had not taken this large Tree Pipit's egg out of the nest of a Tree Pipit (Anthus arboreus); if I myself had not taken out of the nests of the Red-backed Shrike (Lanius collurio) this reddish and this green-greyish peculiarly marked Cuckoo's egg, one might indeed entertain doubts whether this variously-coloured collection—these green eggs, with and without markings; these on white, grey, green, greenish, brownish, yellowish, reddish, and brown-reddish ground; these grey, green, olive green, ash grey, yellow brown, yellow red, wine red, brown red, dark brown and black; these spotted, streaked, speckled, grained and marbled eggs could one and all be the eggs of our Cuckoo! And yet this is indeed the fact!” How different this from the much more cautious and limited statement of Professor Newton, first quoted, which would entirely sweep away some of these varieties, especially those resembling the eggs of the Redstart or the Hedge-Sparrow, for the eggs of these two species do not differ much from each other, and what might be said of the eggs of the one would apply equally to those of the other; yet these are two of Dr. Baldamus' selected species, for, a little further on, he gives a list of the various species from the nests of which Cuckoo's eggs have been taken resembling those of the foster-parent. Of the eggs of the Redstart he says:—“These four specimens, which were found in the nests of Ruticilla phœnicurus, are all of a light-green ground colour; two of them have the larger and more or less brownish spots, which on one of them form a zone; the third has similar markings, but only sparingly scattered over the whole surface, whilst the fourth is without any marking at all—herein it is identical with one in the possession of Dr. Dehne, which is uniformly light-greenish blue, without any markings whatsoever.”