The Egg of the Long-tailed Cuckoo (Eurodynamis taitensis)
[Read before the Canterbury Philosophical Institute, 1932; received by the Editor, December 15, 1935; issued separately, September, 1936.]
The long-tailed cuckoo is by no means an uncommon bird in some parts of New Zealand to-day and it appears to have been even more plentiful in the past; but there is something of a mystery surrounding its egg. Buller1 describes an egg forwarded to him by Rev. R. Taylor, Wanganui, some years prior to 1888 as “almost spherical in shape, with a slightly rough or granulated surface; it is of a pale buff or yellowish-brown colour and measures 1.25 inches in length by 1.15 in breadth.” He further says, “A specimen in the Canterbury Museum taken by Mr Smith from a warbler's nest at Oamaru in November, 1885, corresponds exactly with mine (which is now in the Colonial Museum at Wellington) except that it is slightly narrower.” Buller gives in a footnote to a description from W. W. Smith of an egg supposed to belong to this cuckoo and found in the nest of a wood-robin, “It was almost round in shape, with a deeper shade of colour than the specimen in the Canterbury Museum. Smith reports that this egg was allowed to hatch out and a young long-tailed cuckoo was the result.” Potts2 describes an egg from the Wellington Museum as “nearly round in shape, with the surface rough, of a pale buff colour; it measures one inch three lines in length; with a breadth of one inch one and a-half lines.” As the description is the same, one may conclude that this is the egg from Wanganui referred to by Buller. Hutton and Drummond3 describe the egg as “brownish-olive sometimes clouded with brownish-grey; length 0.7 inches.” Fulton4 went exhaustively into the habits of the long-tailed cuckoo and, describing a nest sent to him, says, “The nest on examination proves to be that of the tomtit (Myiomoira macrocephala), and contains three tomtits' eggs and one strange one. That which I think is undoubtedly the egg of the kohoperoa, for I can refer it to no other species, is white with purplish brown speckles becoming thicker and darker at the larger end. It is something like that of the canary (Mohua ochrocephala) but more elliptical in shape—I should call it ovoidoelliptical—and its length is 0.94 inches and its breadth 0.7 inches.” Oliver5 describes the egg as “broadly elliptical pale buff, 32 × 27 mm.,” but did not remember when I questioned him whether he had seen the egg or had taken Buller's description.
Now from the foregoing Smith's description of the egg seen to hatch out would appear to settle the question of the identity of the long-tailed cuckoo's egg, and yet I am not satisfied that it does
[Footnote] 1 W. L. Buller, Birds of New Zealand, vol. i, p. 131, 1887–1888.
[Footnote] 2 T. H. Potts, Oology of New Zealand, N.Z. Jour. Sci., vol. ii, p. 477, 1885.
[Footnote] 3 F. W. Hutton and J. Drummond, Animals of New Zealand, p. 126, 1904.
[Footnote] 4 R. Fulton, The Long-tailed Cuckoo, Trans. N.Z. Inst., vol. 36, p. 121, 1904.
[Footnote] 5 W. R. B. Oliver, New Zealand Birds, p. 426, 1930.
so. It is a very general rule that the eggs of different species of birds of the same genus are proportional to the size of the birds which lay them. Now the egg of the Australian species of Urodynamis, which is a bird much larger in the body than the New Zealand species, is not so large as the egg ascribed by Buller to Eurodynamis taitensis. Further, although cuckoo's eggs are quite often considerably larger than those of their dupes, there must be some limit to the disproportion, and it seems to me that the egg described by Buller is altogether too large to be imposed on a warbler, creeper, or tomtit.
In September, 1909, I found an egg in a deserted nest of a whitehead (Mohua albicilla) at Silverstream, Wellington. The nest had been subjected to much rain and the egg was somewhat stained by contact with it, but not badly. Its ground-colour was creamy white with purplish brown markings more thickly distributed at the larger end; it measured 23.5 × 17 mm. I could not ascribe this egg to any New Zealand bird, either native or introduced, other than the long-tailed cuckoo, and, accepting as I then did Buller's description of the cuckoo's egg, I had to rule that out also. Last year I went with a friend to Jacques Lee's Island, off Stewart Island. We found numerous long-tailed cuckoos as well as the following Passeres: tui, bell-bird, robin, tomtit, creeper, fantail, warbler and waxeye. Creepers were very plentiful, and on the second day of our stay we found a creeper's nest with a young long-tailed cuckoo in it. This is of considerable interest, for when Fulton suggested that the long-tailed cuckoo used creepers as foster-parents for its young Buller* scouted the idea. Later on we found a creeper's nest with two eggs in it, one of which measured 19.5 × 15 mm. and obviously belonged to the creeper. The other measured 22.75 × 17.5 mm., was creamy white in ground-colour with purplish brown markings—more numerous at the larger end and with underlying markings of grey. These eggs were quite fresh, but the creeper deserted the nest after sitting for one day without laying any more eggs. In February I again went to this island for a week and found a creeper's nest with one egg in it, which had been deserted for some days. This egg measured 23.5 × 17 mm. and was similar in colouring to the one taken from the creeper's nest two months previously, though the creamy tint of its ground colour was slightly more pronounced. One day on this island we found a robin's nest, apparently deserted, containing one egg, which at a cursory glance I put down as a robin's egg. I removed some dead leaves that had fallen into the nest and left the egg to see if the bird would return to it; but next day the egg was taken from the nest, probably by a cuckoo, for we knew these birds were doing extensive nest-robbing on this island. Since finding the other two cuckoos' eggs there, I believe that this also was a cuckoo's egg, and that the robin had deserted the nest because the cuckoo had visited it. Guthrie-Smith records a robin's deserting its nest because a long-tailed cuckoo had visited it; Fulton gives an account of a deserted nest with an egg which he thought was probably this cuckoo's, and the whitehead's and creeper's nests which I have found deserted with
[Footnote] * W. L. Buller. Supplement to the Birds of New Zealand, vol. ii, p. 100, 1905.
cuckoos' eggs in them all point to the fact that some birds are apt to desert their nests once they have been sullied by the presence of a long-tailed cuckoo.
If the long-tailed cuckoo victimises the robin as stated by Smith, and as is indeed quite likely, its eggs, owing to their resemblance to those of the robin, would probably be passed over by anyone who did not examine them closely. They are slightly smaller than the usual run of robins' eggs and their markings are more sharply defined. The outstanding difference between the two eggs, however, is in the texture of the shell, the cuckoo's being thicker and very much harder than a robin's. The surface of the cuckoo's egg is smooth and possesses a slight lustre.
Since writing the foregoing I have seen three eggs collected by Mr A. Portman, of Ravensbourne, Dunedin. Two were in nests of song-thrushes and one in a greenfinch's. All three correspond in size, colouring and pattern of their markings with the eggs above described. Two of them are similar in shape, but the third is rounder. All three of these eggs were found in a gully inhabited by long-tailed cuckoos, but no robins.
To sum up the evidence in favour of the eggs I have described being those of the long-tailed cuckoo: The egg is the size one would expect, using the Australian Uropdynamis and its egg as data for comparison. The egg I found at Silverstream in a whitehead's nest could not have belonged to any other bird, as there were no robins anywhere in the district, even supposing that, had there been, one would have laid in a whitehead's nest. On Jacques Lee's Island long-tailed cuckoos were parasiting creepers, as is shown by their young in the creeper's nest, so the two strange eggs in the creepers' nests which by their texture were not robins' must have been cuckoos' eggs. Fulton found a similar egg in a tomtit's nest, and the three eggs found by Portman can have belonged to no other bird.
Now although the eggs of some cuckoos show remarkable colour and a considerable variation in size, I do not for one moment believe that the long-tailed cuckoo lays eggs as different as those I have described and those which Buller attributed to it. Unfortunately, just as one cannot have a cake and eat it, so one cannot have an egg and let it hatch out. We have no detailed description of the reputed cuckoo's egg in the Canterbury Museum and no measurements of the egg Smith found in the robin's nest and allowed to hatch.
I submit, therefore, that there can be no doubt that the description of the long-tailed cuckoo's egg should be: Ground colour white, tinted with cream or creamy pink, freely spotted and streaked with purplish-brown and having underlying spots of grey, the markings being larger and more numerous at the larger end of the egg. The shape is ovoido-elliptical, and the measurements in mm. of four specimens are 23.5 × 17; 23 × 17.75; 22.75 × 17.5; and 22.5 × 18.
Regarding the egg described by Buller as that of the long-tailed cuckoo it was probably a “pullet” egg of a domestic fowl: the description of the egg is exactly that of a “pullet,” and Buller himself says, “I ought to state, however, that it was obtained from a native and that its authenticity cannot be considered to be quite certain.”