A History of the Birds of New Zealand.
Xenicus Gilviventris. — (Rock-Wren.)
Xenicus gilviventris, Von Pelz. Verh. k.-k. zool.-bot. Ges. Wien, 1867, p. 316.
Xenicus haasti, Buller, Ibis, 1869, p. 37.
Acanthisitta gilviventris, Gray, Hand-l. of B. i. p. 183 (1869).
Acanthisitta haastii, id. tom. cit. p. 183 (1869).
♂ staturâ X. longipedis, sed hallucis ungue maximo distinguendus: suprà pallidè viridis, pileo et dorso superiore brunnescentioribus concoloribus: supercilio albo, haud flavo tincto: subtùs dilutè chocolatino-brunneus, crisso cum cruribus viridescentibus, hypochondriis lætè flavis: subalaribus pallidè flavis.
♀ feminæ X. longipedis dissimilis et hujus mari magis assimilata: suprà ochrascenti-brunnea, uropygio vix viri-descente: tectricibus alarum conspicuè nigris: remigibus brunneis, extùs dorsi colore lavatis: subtùs pallidè isabellina, hypochondriis viridescentibus.
Adult male. Upper parts dull olive-brown, with a greyish gloss, darker on the forehead and crown, and tinged on the back, wing-coverts, and rump with yellowish green; sides of the head dark brown, with a narrow superciliary streak of fulvous white, widening above the ears; underparts delicate purplish brown, with a silky appearance, and fading into fulvous white at the base of the lower mandible; the sides of the body lemon-yellow; wing-feathers brown, the primaries margined on their outér webs with dull olive, the secondaries with an apical spot of fulvous on their outer webs; tertials and the lesser wing-coverts black, forming a conspicuous triangular spot; inner lining of wings pale yellow; tail-feathers dull olive. Irides and bill blackish brown; tarsi and toes pale brown; claws darker. Total length 3·75 inches; wing, from flexure, 2·1; tail ·75 (nearly two thirds of it being concealed by the coverts); bill, along the ridge ·4, along the edge of lower mandible ·6; tarsus 1; middle toe and claw ·9; hind toe and claw ·9.
Adult female. Differs from the male in having the plumage of the upper parts dull yellowish brown, shaded with umber on the crown, and tinged with yellowish olive on the wings and rump; the superciliary streak less distinct; and the underparts pale fulvous, stained on the sides of the body with lemon-yellow.
Obs. It will be necessary to obtain a larger series of specimens than is at present available, and to make a closer investigation of the subject, before the differences supposed to be characteristic of the sexes (both of this and the preceding species) can be considered finally determined. It is probable that the colours undergo some change in the progress of the bird towards maturity; and there is likewise reason to suspect that a seasonal change takes place in the plumage of the male.
My first specimens of this bird were received from Dr. (now Sir Julius von) Haast, F.R.S., who discovered it in the Southern Alps, during a topographical survey of the Canterbury Province. In a notice which I communicated to ‘The Ibis’ (I. c.), I described the species as new, and named it Xenicus haasti, in compliment to the discoverer. This name, however, must, in obedience to the inflexible law of priority, give place to Xenicus gilviventris, a description of the species under that title having previously been published by Von Pelzeln, although it had not then reached the colony. Nevertheless I am glad to be able to quote Haast’s account of the bird’s habits as communicated to me at the time:—“It lives exclusively amongst the large taluses of débris high on the mountainsides. Instead of flying away when frightened or when stones are thrown at it, or even when shot page 112 at, it hides itself among the angular débris of which these large taluses are composed. We tried several times in vain to catch one alive by surrounding it and removing these blocks. It reminded me strongly of the habits and movements of the lizards which live in the same regions and in similar localities.”
Another correspondent says that “they move about so nimbly that to procure specimens was like shooting at mice.”
This species is confined to the South Island, being met with in the mountains, at an elevation of 3000 feet and upwards, their range appearing to commence with the snow-line, below which I have never heard of their being found.
Mr. Brough, who sent me a specimen from Nelson, says it was one of five which he met with in February on the very summit of a barren mountain. “They were dodging about among the angular rocks right on the top of the peaks, where there was no vegetation except the so-called ‘vegetable sheep’ (Raoulia eximia), which grows freely enough among the débris or shale.” These birds were, at that time, catching a bright-coloured alpine butterfly, which I have since identified as Phaos huttoni.
Mr. Reischek writes that he found it very plentiful on the top of Mount Alexander, near Lake Brunner, also on Mount Alcidus, near Rakaia forks, “hopping about among the débris grown over with alpine vegetation.” On the heights overlooking Dusky Sound, he found it extremely rare, a circumstance which he attributes to the thousands of rats infesting that region.
Sir J. Hector found it frequenting the stunted vegetation growing on the mountain-sides in the Otago Province; and Mr. John Buchanan, the artist attached to the Geological Survey, met with it on the Black Peak, at an elevation of 8000 feet. There, where the vegetation is reduced to a height of only a few inches, it was constantly to be seen, fluttering over the loose rocks or upon the ground in its assiduous search for minute insects and their larvæ.
It is worthy of remark that in this species the claw of the hind toe is considerably more developed than in the tree-frequenting X. longipes—even exceeding the toe in length—a modification of structure specially adapted to the peculiar habits of the bird, which differ from those of the former species consistently with its habitat. They hunt much on the ground, particularly in wet weather; and will freely visit the explorer’s camp, hopping about on the ground, picking at mutton-fat or any thing of the kind lying outside. The young are fed on insects; and it is amusing to see the old birds coming to the nest, sometimes with a dragon-fly almost as large as its captor, and dividing it among the brood.
Mr. W. W. Smith informs me that on one occasion he collected twelve of these birds, and that the stomachs of all of them contained the minute chrysalids commonly found among fallen leaves and other decaying vegetation.
The nest, which is a more finished construction than that of the Bush-Wren, is placed in a sheltered crevice among the loose rocks or débris of the mountain. One found under these circumstances by Mr. Brough in the Nelson district, on Sept. 24, contained five eggs. This nest, which is now in my collection, is of a rounded form, laterally compressed, and measuring five inches in its widest diameter. It is composed externally of wiry rootlets, intermixed with very small twigs and dry leaves. The entrance is on the side, being a perfectly round aperture about an inch in diameter. The interior of the nest is lined with soft feathers.
The egg (of which I have a single damaged specimen) is ovoido-elliptical in form, measuring ·7 of an inch in length by ·5 in breadth, and is perfectly white, with a slightly polished surface.