The New Zealand Saddlebacks
[Read before the Canterbury Philosophical Institute, 1934; received by the Editor, December 15, 1935; issued separately, September, 1936.]
When Buller wrote the first History of the Birds of New Zealand he described the jack-bird* as the young of the saddleback, but in his second edition of the same work he gives it rank as a separate species under the name Creadion cinereus. He did this because, although the saddleback was a common enough bird in the North Island, the jack-bird had never been seen there. Moreover, Reischek had reported that on Hen Island he had seen saddlebacks feeding young that had just left the nest, and that these young resembled their parents in coloration. Further, Reischek had colleced a number of jack-birds in the South Island, and on dissection he found their reproductive organs well developed, and hence decided that they were adult birds. Dr. Otho Finsch and Capt. Hutton said that Buller was quite wrong in describing the jack-bird as a separate species, but apparently did not explain its absence from the North Island. Later Hutton accepted the jack-bird as a valid species.
Matthews and Iredale were, I believe, the first to separate the North Island and the South Island birds into separate species, describing the jack-bird as the young of the South Island bird. Guthrie-Smith regarded the jack-bird as the young of the South Island saddlebacks because its wattles were smaller and it was not apparently breeding when the saddlebacks were. Oliver treats the saddlebacks of both islands as identical and the jack-bird as the young of both. He says, “In the South Island it is clear from the observations of Potts and Guthrie-Smith that the brown stage lasts about a year. Mrs M. M. Moncrief seeks to reconcile these diverse views on the theory that the length of time the immature retains its brown plumage varies in different localities, being longest in the South Island, shorter in the North Island south of Auckland and suppressed altogether on Hen Island. This may be true, but not to the extent supposed by Mrs Moncrief, for birds from Hen Island reared on Kapiti pass through the ordinary brown stage, and it is inconceivable that it could have been acquired as a result of transferring the birds the season before. Undoubtedly, therefore, the saddleback in all parts of New Zealand passes through a brown immature stage, but in the North Island it seems to acquire the adult plumage earlier than in the South Island.”
There is no justification for the suggestion that the period during which the saddleback retains its juvenile plumage becomes shorter the further north its habitat, for Buller† records a young bird in “saddled” plumage from Stephen Island, in Cook Strait. Oliver was misled by faulty observation on the part of the caretaker
[Footnote] * Throughout this paper I shall for simplicity refer to the young of the South Island saddleback as the “jack-bird.”
[Footnote] † W. L. Buller, Supplement to the Birds of New Zealand, vol. 2, p. 161, 1905.
of Kapiti Island, who said that the saddlebacks introduced there from Hen Island bred next year, and the young were jack-birds.
It is fortunate that both North Island and South Island forms are still in existence, and that even at this late date the confusion concerning them can be cleared up. It is a most extraordinary thing that none of the early observers seems to have seen the young of these birds in the nest or, at any rate, to have recorded having done so. On an island off Stewart Island Guthrie-Smith found nests with young; but they did not have feathers sufficiently developed to enable one to describe their colour. The North Island form is now extinct on the mainland, and the South Island form is at best extremely rare on the mainland; indeed, the only indication available to me that it still exists is an observation by Major R. A. Wilson, who thinks he heard one some three years ago in South Westland.
On three islands to the south-west of Stewart Island, and possibly on two others nearby, the saddleback is quite a common bird. In 1931 I spent five weeks here and found a total of about forty of their nests (building, with eggs and with young). The birds begin to nest in the later part of October and their nesting season extends to the end of December at least. The first (juvenal) plumage of the young is an almost uniform olive-brown becoming reddish-brown on the rump upper and lower tail-coverts; the primaries and secondaries and the retrices are brownish-black. The colouring of the breast is very slightly paler than that of the back. The wattles are small. I had an opportunity of watching the interesting formation of these wattles. Wishing to obtain photographs of the adults, I put a piece of wire-netting over the top of a hollow stump in which was a saddleback's nest with two feathered young just about to fly. At this stage the fold of pale yellow skin at the angle of the gape is very prominent; indeed, it is so from the time the chick is hatched, as is the case with the common starling. It will give a good idea of the state of development of the young when I say that their tail-feathers were about half their adult length. At this stage the soft skin at the gape begins to contract at its forward end until the skin at the angle is sticking out almost as a point, which then folds downwards, forming the small wattle of the juvenile, the whole process taking between a week and ten days. One would naturally expect the young to go through a fairly complete body-moult in the autumn, but I am not sure that they do. They certainly moult more or less sporadically through the remainder of their first year, for in November and December, when they would be rising twelve months old, some of them are still coloured as in their juvenal plumage save that the rump and tail-coverts are a brighter brown, while others are showing varying quantities of black feathers on the head, neck and breast. From dated specimens I have examined I am inclined to think that some of the birds may take three years to attain full adult plumage.
I believe that occasionally a bird in the jack-bird plumage breeds, for I saw one day a family party of three—a male saddle-back, a juvenal-plumage jack-bird and a yearling jack-bird feeding in a tree-top. The cock bird fed the young, which squatted on its
perch with wide open mouth and quivering wings; and presently he hopped up to the other and gave it a grub, which it accepted in the manner of an adult hen, taking the food from the other bird's beak, standing erect the while and not quivering its wings. I watched these birds for a long time, and feel sure that the yearling jack-bird was the mate of the cock saddleback and the mother of the young bird. Whether this was the case or not, the reproductive organs are, as Reischek said, quite well developed in jack-birds twelve months old.
The young of the North Island saddleback is of similar colouring to its parent, but there are certain differences by which it can be identified. Its black feathers fade to a brownish-black within a few months, and its wattles are much smaller. The brown “saddle” is not so bright as that of the adult and there is no pale edging to its forward part. As single birds with rather dull plumage and very small wattles are to be met with in November and December, it seems that the North Island as well as the South Island bird does not breed as a rule until it is two years old.
G. M. Matthews (Ibis, p. 90, 1933) writes as an addition to his Systema :-
“P. 856. Read Philesturnus carnuculatus carunculatus (Gm.).
“Distribution: South Island.
“And Philesturnus carunculatus refusater (L. & G.).
“Distribution: North Island.
“In the North Island bird the young practically resemble the adult from the nesting plumage; whereas the South Island birds go through at least one moult from the uniform cinereus chick before they assume adult plumage, which they do when twelve months old.”
I do not know that any writer has yet suggested that the adult North Island saddleback can be distinguished from the South Island bird, but this can be done. In the North Island bird there is a line of pale feathers between the brown and the black across the shoulders. This light band varies in intensity in different individuals, but is present in all the adult North Island saddleback skins I have examined either from the mainland or outlying islands, and is quite noticeable in live birds in the bush. Further, the bill of the North Island bird is narrower and more pointed towards the tip when viewed from above. Generally speaking, it is also a slightly smaller bird, though the measurements in a big series overlap; but by its colouration and the shape of its bill it can be identified. The young of the North Island species has no light band on the shoulders between its brown and black, and in this respect it resembles the South Island bird; but its duller colouring, smaller wattles, and shape of its bill are characters by which it may readily be indentified. It remains to be said that the eggs of the two species are similar, going through the same range of colouring, though those of the North Island bird are on the average smaller than those of the South Islander.