IN TOUCH WITH NATURE.

Otago Daily Times, Issue 15826, 26 July 1913, Page 15

IN TOUCH WITH NATURE.

NOTES ON NATURAL HISTORY IN

NEW ZEALAND.

(Bl Jix*s Drummond, F.L.8., F.Z.S.)

The general publio is not greatly interested in.the somewhat subtle distinctions systematists make between different species of animals, but as & puzzled correspondent hag asked me to enlighten him in regard to the position o£ kiwis witn dark plumago which he has seen in the North Island on several occasions, ■ I aan giving the subject the whole of this week's columm Most systemaliate who have dealt with the kiwis as a group recognise only' one North Island species, which is named Apteryx mantelli. This is the common brown, or rafoua kiwi, seen moat frequently. In several North Island districts, notably Taranaki, however, kiwis have been found with brown-ish-black feathers, like those to which the correspondent who has opened the subject refers. Should these kiwis be placed in a separate species, or are they merely members of the species mantelli, with abnormal colours?

The question involves a definition of the word species. Roughly, it is used in, science in the Bame way as "kind" is applied to animals in ordinary conversation. It has no fixed rules, and there are wide differences of opinion amongst scientists as to what it stands for. Some insist upon establishing a species where others recognise no specific differences ■whatever. In many branches of research this has resulted in workers being divided into two "splitters," who are inclined to mako many species, and ''stampers," who make species only where differences are strongly marked. Haeckel has illustrated the . difference of opinion in this respect by the case of calcareous sponges, of which, a scientist may make three species or 21, or 289, or 591, according ias attitude towards the "splitters " and the "slumpers," and the distance he is prepared to go with one section or the other. The general idea is that members of a species should have a. very closs resemblance, and possess characteristics which were handed down _to all of them by their parents, and which they, in turn, will pass on to their progeny. The characters ithat mark a species must be easily recognised, and they must be constant, which means that they must be handed down from one generation to another. After all, however, a species is only a conception, a convenience in grouping together individuals which resemble one another so closely that a common name mav be applied to them all. It is the individuals themselves which interest us, and it is their habits and structure that are most worthy of attention.

It is not surprising, in the circumstances, that the dark kiwis of the North Island have beeu the subject-of much discussion. Sir Walter Buller, in his "Supplement," separated them from the common North Island species, and applied _to them the specific name "bullori," which was originally proposed for them by Dt R. B. Sharpe, of the British Museum, some years previously. Sir Walter states that Sir James Hector -was the first.person to call his attention to _ the existence- of a dark race of kiwis, telegraphing to him from Gisborne to examine a live specimen that was passing through Wellington on a Home-ward-bound vessel. Later en, Sir Walter obtained seven specimens from the Waitara district. He found that • they showed varying shades of colour. The brown predominated in some, but on the whole they had a very different appearance from that of the ordinary North Island kiwi. He therefore split the species, leaving the common brown rufous kiwi with the specific name "mantelli," and giving the blackish-brown birds the name "bulleri," which, by the way, is the Latinised form of his own name.

Since Sir Walter Buller's time a fairly large number of specimens of the dark kiwis have' come under observation. Nearly all of them, I believe, have come from Taranaki. As Sir Walter Buller and Dr Sharpe point out, the plumage is distinctly darker than the plumage of the common kiwi. It is very doubtful, however, if they were justified in creating a separate species for these birds._ The colouration of the North Island kiwis is very inconstant. A short time ago I saw a skin which is brownish-wey, iiistead of the brownish-black described by Sir Walter Buller. On its flanks and breast it has spots of amber, caused by the lighter colour at the tips of some of the feathers. There is light-grey on the sides of the head, the lores, the throat, and the forehead, shading off into dark-grey on tlie crown. It is a male, and the male kiwis of the North Island are distinguished by pale-brown legs and feet, ' sometimes whitish, but this specimen distinctly black legs, feet, and claws, evidently anabnormal colouration- Other North Island kiwis have shown a tendency towards erythrism, or red colouration. This is so marked that the Maoris have a term, "kiwi-kura," or rod kiwi, for these reddish birds. In some instances they are a dull brick-red; in other instances they are chestnut; in others they come closer to the typical rufous-brown members of the species. There is no suggestion that the red kiwis should bo placed in • a separate species, and there does not secin to be any reason why a specific distinction should be made in favour of the dark kiwis. In regard to both the red and the dark there are intermediate specimens, showing gradations back to the common type. There is, therefore, no real line of demarcation, and it has not been shown that the colouration is passed on from one generation to another. The position seems to be a case of heterochrosis, or abnormal colouration, caused by an exceptionally large proportion of black pigment in the feathers in one instance, and of red pigment in the other instance. Heterochrosis is not. uncommon among birds, but it usually shows itself in isolated cases. Albinism, or whiteness, as a- form of it, caused by a partial or complete absence of pigment; melanism, or black colouring, a.s in the case of the dark kiwis of the North Island, is another form.

The position of the grey kiwis of the South Island in regard 'to classification, also, is somewhat unsatisfactory at present. Some years ago, for instance, the Hon. Walter Rothschild established the species Apteryx commonly known as the spotted kiwi, and described by Sir Walter Buller in his "Supplement" as the West Coast kiwi. It is like the grey kiwi, Apteryx oweni, having a grey plumage spotted with yellowish white, the spots forming bands over the plumage, but it is larger, and the alternate black bars on the feathers are bolder and more distinct, and stand out more conspicuously. The species was established on a single specimen Mr Rothschild received alive at his place at Tring, England. It was sent to him by Sir Walter Buller, who bought it from Mr Bills, or Dunedin, who, in turn, obtained it from Dusky Sound. The plumage, besides resembling that of the grey kiwi, is also like that of the great spotted kiwi, Apteryx Haasti.\ Sir Walter Buller expresses an opinion that Mr Rothschild was justified in making a species for this Apteryx occidentals, but Mr Rothschild himself evidently is not. sure of his ground. In a letter to me, describing kiwi specimens in his museum, he said that "my series is very complete, and the only point not yet elucidated is the exact status of my occidental; it is remarkably different from the true oweni, but in some cases occurs together with that species and Haasti, so it may be a hybrid between the two latter. This could only be settled by breeding them in confinement.