Art. XVIII.—Note on Gerygone flaviventris.
[Read before the Wellington Philosophical Society, 7th August, 1875.]
The last volume of “Transactions of the New Zealand Institute,” contains, at page 524, an interesting note by Mr. Justice Gillies, on the habits of
Gerygone flaviventris. The learned author describes, in very pleasing language, a nest of this warbler, which he met with at the Bay of Islands, when travelling in company with Dr. Hector and Professor Berggren, and he concludes with these words:—“How the long-tailed cuckoo (Eudynamis taitensis) can, as stated by Dr. Buller, (‘Birds of New Zealand,’ p. 75) deposit its eggs in such a nest, I can scarcely understand. On the 22nd instant (October), one of my children discovered, under a large Cupressus macrocarpa, in my garden, a specimen of the Eudynamis taitensis, recently killed, apparently by a hawk. It would have been impossible for the Eudynamis to have entered the opening in the nest of the Gerygone.”
On referring to the page of my work, cited above, it will be seen that, so far from making the supposed statement, I expressed a very decided opinion to the contrary. My language was as follows:—“Very little is at present known of the breeding habits of this species (Eudynamis taitensis). As I have mentioned above, it is parasitical; but to what extent, is not yet determined. My own belief is, that it performs itself the duty of incubation, and then abandons its young to the grey warbler, which instinctively accepts the charge, and caters untiringly for its support. In the first place it is difficult to conceive how a bird, of the size and form of the Long-tailed Cuckoo, could deposit its egg in the domed nest of the last-named species, and, even supposing it did, it would seem almost a physical impossibility for so small a creature to hatch it, and, again, even were this feasible, it is difficult to imagine how the frail tenement of a supension-nest could support the daily-increasing weight of the young cuckoo. Over and above al this, there is the significant fact that I once shot an adult female of the present species, in which the underparts were quite denuded of feathers, as if the bird had been long incubating. Strange as such an hypothesis may appear, we are not altogether without a parallel instance in bird-history; for, in the case of the Chrysococcyx smaragdineus, of Western Africa, it is alleged that this cuckoo hatches its single egg, and then, utterly unmindful of its parental obligations, casts the care of its offspring on a charitable public, and that almost every passing bird, attracted by the piping cry of the deserted bantling, drops a caterpillar, or other sweet morsel, into its imploring throat. My artist, Mr. Keulemans, assures me that he often witnessed this himself during his residence on Prince's Island.”
It will be seen, therefore, that the line of my argument was entirely opposed to the theory of the Eudynamis entering the nest of Gerygone. Where it lays and hatches its egg I do not pretend to say; but that the young cuckoo is attended and fed by the grey warbler, is a fact established beyond all doubt. The plate facing page 73 of the “Birds of New Zealand,” which represents this little bird performing this parental office to its foster-
child of another species, and about ten times its own size, is no fanciful representation, but a true picture of bird life.