Art. XVI.—On a Pure-white Form of Anas superciliosa Gmel.
[Read before the Otago Institute, 4th August, 1914.]
Albinism in a greater or less degree is a not uncommon phenomenon among New Zealand birds. The occurrence, however, of a pure-white form of the common grey duck (Anas superciliosa) is of sufficient interest to justify its being put on record.
Already several specimens of this species showing partial albinism and other variations have been recorded. Dr. Buller, in vol. 7 of the “Transactions of the New Zealand Institute,” at p. 224, mentions a case of partial albinism, but seems to think that the specimen was possibly a cross with the common domestic duck. He has also, in the second edition of “Birds of New Zealand,” mentioned several cases of partial albinism, and states that his son reported having seen a pure albino in a wild state. The specimen was not, however, procured. Mr. W. W. Smith * also describes several aberrant forms of variation tending to albinism. Mr. T. W. Kirk † records a similar instance in the case of the brown duck (Elasmonetta chlorotis).
The specimen that I have now set out to describe was shot by Mr. George Moffatt on the 21st June, 1914, at Cattle Flat, on the Mataura River. From what he tells me, it was associated with a flock of grey ducks, and had been seen several times by him. It was a good flier, and, except for colour, was not distinguishable from its associates, its flight and habits being the same. Immediately on its receipt by me I sent it to Dr. Benham, who agreed that it seemed to be an albino form of Anas superciliosa. He has since kindly sent me formal measurements of the bird, which are sufficiently near to those recorded by Buller to make identification practically certain. The following are the measurements taken:—
|Total length from tip of beak to base of tail-feathers||20|
|Length of wing-quills||10|
|Length of bill along edge of upper mandible||2.25|
|Length of bill along edge of lower mandible||2.375|
|Length of tarsus||1.75|
|Length of mid toe and claw||2.5|
The bird, on dissection, has proved to be a male. Its plumage throughout is pure white; eye, dark brown; legs and bill, yellow. In point of size and shape it differs in no way from the typical wild grey duck. This interesting specimen is in good condition, and has been stuffed and mounted. The owner has generously decided to present it to one of the public museums of New Zealand. For some time at least, if not permanently, it will be deposited in the Otago Museum.
Shortly after the above paper was read Dr. Benham kindly sent me the following communication which he had received from Mr. W. O. Kempthorne, of “Redmount,” Key, via Lumsden. As the letter affords a
[Footnote] * “On New Zealand Ducks,” Trans. N.Z. Inst., vol. 29, 1897, p. 252.
[Footnote] † “On some Additions to Birds in the Colonial Museum,” Trans. N.Z. Inst., vol. 13, p. 235, 1881.
plausible explanation of the occurrence of the above-described albino duck, I gladly publish it as received:—
Writing on the 16th August, 1914, Mr. Kempthorne says, “I have just noticed a paragraph on page 9 of Otago Witness of the 12th August about an albino wild duck having been shot. I dare say you will be interested in a very probable explanation of this curiosity. At my mother's place (“Parkdale,” Heriot) there is a large pond which for twenty years has been a sanctuary for the wild duck (it being on private property, and my mother's wishes that no shooting shall be allowed, have made it such). In wet weather hundreds of ducks gather there, and the ducks bred there make it their home. For years there were white tame ducks also, but they dwindled in number until only one drake remained. This drake mated with a wild grey duck that was unable to fly (or could fly very little) and necessarily had to live entirely at the pond. I remember four or five years ago coming on a mixed clutch of ducklings (whites and greys), but after seeing them two or three times I never saw them again, and concluded that a weasel had accounted for them. On a recent visit to “Parkdale” (three weeks ago) I saw an albino wild duck, and my brother said there were more than one. It could fly, as I made it my business to frighten it and see. Evidently the tame white drake and the crippled wild duck had mated again, and their progeny had lived. The distance between Heriot and Mataura in a direct line would be thirty-odd miles, and this would not be an excessive distance for the flight of a wild duck. The tame Indian runner duck and the wild grey duck mate without trouble, but this is the only case I have heard of a white tame duck mating with a wild grey duck. It would be interesting to test the case again on the wild grey ducks in the Botanical Gardens. The two ducks would have to be shut together continuously for a lengthened period to ensure a satisfactory result.”