A History of the Birds of New Zealand.
Gerygone Flaviventris. — (Grey Warbler.)
Curruca igata, Quoy et Gaim. Voy. de l’Astrol., Zool. i. p. 201, pl. xi. fig. 2 (1830).
Acanthiza igata, Gray, in Dieff. Trav. ii., App. p. 189 (1843).
Gerygone flaviventris, Gray, Voy. Ereb. and Terror, p. 5, pl. 4. fig. 1 (1844).
Gerygone igata, id. op. cit. p. 5 (1844).
Gerygone assimilis, Buller, Essay on Orn. N. Z. p. 9 (1865).
Acanthiza flaviventris, Gray, Hand-1. of B. i. p. 219 (1869).
Native names.-Riroriro and Koriroriro.
Ad. suprà grisescenti-brunneus, dorso et uropýgio cum supracaudalibus olivaceo lavatis, his lætiùs tinctis: tectricibus alarum remigibusque brunneis, extùs angustè olivaceo limbatis: rectricibus cinerascenti-brunneis versùs apicem conspicuè nigricantibus, duabus externis maculâ anteapicali albâ notatis, reliquis ad apicem pogonii interni albo maculatis: facie laterali guttureque toto sordidè cinereis: corpore reliquo subtùs albicante, abdomine imo et hypochondriis flavido tinctis, his etiam paullò olivascentibus: rostro et pedibus saturatè brunneis: iride rubrâ.
Juv. similis adultis, sed coloribus dilutioribus.
Adult male. Upper parts brownish grey, tinged on the back with olivaceous brown; throat, fore part of neck, breast, and sides cinereons grey; abdomen and under tail-coverts white, the former slightly tinged with yellow; primaries dark brown, paler on the inner webs; tail-feathers dark brown in their basal, almost black in their apical portion, and, with the exception of the two median ones, having an angular white spot near the tip on their inner webs. The plumage is sooty black at the base, but this is only observable on moving the feathers. Irides red; bill, tarsi, and toes dark brown. Total length 4·5 inches; extent of wings 6; wing, from flexure, 2·12; tail 2; culmen ·3; tarsus ·75; middle toe and claw ·5; hind toe and claw ·75.
Female. Similar in plumage, but of smaller size.
Young. In the young bird the tints of the plumage generally are paler and there is an entire absence of the yellow tinge. Irides brown.
Obs. In some adult examples the measurements are slightly larger than those given above, there is an absence of the yellow tinge on the abdomen, and the white spot on the lateral tail-feathers is terminal.
Note. A figure of this bird in the act of feeding a young Cuckoo will be found on the Plate representing Eudynamis taitensis. The illustration given in the ‘Voy. de l′Astrolabe’ is scarcely recognizable.
In the warm sunlight of advancing summer, when the manuka-scrub is covered with its snow-white bloom and the air is laden with the fragrance of forest flowers, amidst the hum of happy insect-life, a soft trill of peculiar sweetness—like the chirping of a merry cricket—falls upon the ear, and presently a tiny bird appears for an instant on the topmost twigs of some low bush, hovers for a few moments, like a moth before a flower, or turns a somersault in the air, and then drops out of sight again. This is the Grey Warbler, the well-known Riroriro of Maori history and song.page 45
This little bird, of sombre plumage and unobtrusive habits, is an interesting species, whether we regard it merely as the familiar frequenter of our gardens and hedgerows, or, more especially, as the builder of a beautiful pensile nest and the foster-parent of our two parasitical Cuckoos (Eudynamis taitensis and Chrysococcyx lucidus). It belongs to a group of which there are numerous representatives in Australia, and its habits are in no way different from those of its relations.
It is plentiful in every part of New Zealand, and appears to be as much at home in the woods as in the open scrub. I have seen it hunting for its minute prey in the leafy tops of forest trees, the tawa being its favourite resort, probably on account of some special kind of insect food. On one occasion, after very cold weather, I picked up a dead one at the foot of an aged kauri tree, with a smooth trunk fully seventy feet in height. In the Hot Lakes district I have found it flitting round the steaming geysers, apparently unaffected by the sulphur fumes, and catching the minute flies that are attracted thither by the humid warmth. Down by the sea-shore its note may be heard in the low vegetation that fringes the ocean beach; whilst far up the mountain-side, where the scrub is scarce and stunted, it shares the dominion with the ever-present Zosterops. Its sweet trilling warble is always pleasant to the ear, being naturally associated in the mind with the hum of bees among the flowers, and the drumming of locusts in the sunshine. It becomes louder and more persistent in the spring-time; and “Kua tangi te riroriro” has become a sort of watchword among the Maoris, signifying “Planting-time has commenced: let us be up and doing.” I remember the late Sir Donald McLean commencing one of his most successful Maori speeches with those figurative words, using them of course in a political sense *.
Its food consists of minute flies and insects and their larvæ, in the eager pursuit of which it appears to spend its whole time, moving about with great agility and uttering at short intervals a note of much sweetness, though of little variety. The bird is easily attracted by an imitation of this note, however rudely attempted, and may be induced to fly into the open hand by quickly revolving a leaf or small fern-frond, so as to represent the fluttering of a captive bird. Layard compares the note to the creaking sound of a wheel-barrow; and I have sometimes heard it so subdued and regular, as to be scarcely distinguishable from the musical chirping of the pihareinga or native cricket.
When resting on a twig, it has a habit of flipping its wings after the manner of a Goldfinch. Its ordinary flight is in short undulations with the tail outspread, showing the markings on the lateral feathers.
Where the rank growth of bracken covers the open land, mixed here and there with the flowering Leptospermum and blending its sombre tints with the dark-green clumps of tupakihi forming together a close thicket over which the wild convolvulus twines itself and exhibits its pendent flowers of pink and white—here the Grey Warbler has its home in absolute security, and here in some shady recess it hangs its pear-shaped nest and rears its little brood. It builds a large and remarkably ingenious nest, in which it lays from three to six eggs, and, as I am inclined to think, breeds twice in the season. The construction of the nest, which is of great size as compared with the bird, occupies of necessity a considerable time. In one instance noted, I observed the birds collecting materials for their work towards the end of August, and the young did not quit the clump of climbing-rose in which the nest was placed till the first week in October.
Selected on accóunt of its unwearied industry, or because of the peculiar fitness of its warm domed nest for the nurture of a semitropical species, this little bird is the willing victim of our two migratory Cuckoos, the Warauroa and Koheperoa—the former of which, at any rate, deposits its egg in the nest of this species, while both of them delegate to this tiny creature the task of rearing their young.
* “I hea koe i te tangihanga o te riroriro”? (Where were you when the Riroriro began to sing?): a proverb applied to a lazy man who neglects his planting.
I have found the intrusive egg of the former in the nest with those of the Grey Warbler, and I have frequently observed the voracious young Cuckoo being attended and fed by the foster-parent, but I have never seen the young of these birds together. Either the parasitic egg being the first hatched, the others are neglected and allowed to perish, or the intruder, finding the accommodation insufficient, by virtue of his superior size and strength casts out the rightful occupants and usurps entire possession of the nest.
Although, as already mentioned, the Grey Warbler appears to lay twice in the season*, it would seem that one nest serves the purpose of rearing two broods; for, allowing that the family would require the attention of the old birds up to the middle of October (though probably it would be later), there would not be time to build another nest before the arrival of the Cuckoos to spend the summer with us and to deposit their eggs for incubation. The production of double broods in this case would seem to be a provision of nature to enable this species to maintain its ground, seeing that the demands of the parasitical Cuckoos involve in many cases the loss or destruction of the legitimate offspring. Instead of being scarce, the Grey Warbler continues to be one of our commonest species— a circumstance owing, no doubt, in some measure, to its being a pensile-nest builder, and thus escaping the ravages of the Norway rat, the great enemy to the increase or perpetuation of our indigenous birds.
The young on leaving the nest are extremely nimble and somewhat shy. For several days after quitting their domed cradle they remain in its. vicinity, following the old birds about in a restless manner and emitting incessantly a scarcely audible piping note. On these occasions I have noticed that the birds hunt all day long in a wide circle, with the nest-home as a centre; and they probably take their young family back to it at night for shelter and warmth. The nests of most birds, when the young have flown, are polluted and unserviceable, being easily distinguishable as “old nests;” but this is not the case with the nest of the species under consideration. The cavity or chamber is deeply lined with soft feathers; and to keep the interior clean and pure, the young birds may be seen elevating their bodies to the edge of the orifice on the side of the nest and ejecting the alvine discharge to some distance. Thus the nest is kept in perfect condition for continued use, in the manner suggested, for the rearing of a second brood. At the close of the breeding-season it may be observed that this bird has the shafts of the tail-feathers denuded, often to the extent of a quarter of an inch, the result, no doubt, of its laborious building-operations.
* In further support of my view as to a double brood, I am glad to find room for the following valuable note received from Mr. J. Brough, of Nelson:—“It may interest you to know exactly the time it takes the Grey Warbler to construct its nest. On November 29 I took a nest with five eggs which I had found close to my camp. On December 1 the birds commenced a fresh nest near the site of the old one. I watched them carefully, and will give you the result as entered every night in my diary.— Dec. 2. Showery day; warblers hard at work. Dec. 3. Snow showers; but no interruption in the work. Dec. 4 & 5. Snowing all day, but warblers hard at work from morning till night. Dec. 5. Fine day; birds working diligently. Dec. 6. Another fine day; warblers completed their nest. Dec. 8. First egg laid. Dec. 11. Another egg. Dec. 12. Third egg. Dec. 13. Fourth egg laid, and hen commenced to sit. Whilst the building of the nest was proceeding, I noticed that the male bird undertook the chief part of the labour in collecting and carrying materials, and that the weaving of these materials together and building of the nest was performed almost entirely by the female.”
Since the foregoing was written, Mr. R. B. Sharpe has expressed his belief that the bird brought from New Zealand by the ‘Astrolabe’ Expedition in 1829 (Gerygone igata, Quoy et Gaim.) is a distinct species. Being anxious to determine the point for myself, I lately paid a visit to Paris and examined the type. I was unable to find any character by which it could be distinguished from the common species. It is apparently a young bird with soft plumage; there is no tinge of yellow on the underparts, and the dark grey of the upper surface is somewhat suffused with brown*.
Strictly speaking, according to this view, Gerygone igata ought to take the place of Gerygone flaviventris, owing to its priority over the latter; but, in the first place, the name is a barbarous one and objectionable on that account, and, secondly, I am unwilling to disturb a name that has been in general currency for close upon fifty years.
The two forms of nest above alluded to were thus described in my ‘Essay’ (p. 9):—“That of the smaller species is a compact little nest, measuring about 6 inches by 3·5. It is ‘bottle-shaped,’ full and rounded at the base, and tapering upwards to a point, by which it is suspended. It is composed of a variety of soft materials—spiders’ nests, dry moss, grass, vegetable fibres, &c. The spiders’ nests consist of a soft silky substance, by the aid of which the materials composing the nest are woven into a compact wall, with a smooth and finished exterior. The entrance, which is situated on the side of the nest, is so small as barely to admit the finger, and it is protected from the weather by a very ingenious contrivance. It is surrounded by a protecting rim or ledge, composed of extremely fine roots interlaced or loosely woven together and firmly secured to the groundwork of the nest. This facing is arched at the top so as to form a vestibule or porch, while at the base it stands out boldly from the wall, and is nearly an inch in depth, thus furnishing a firm and secure threshold for the bird in its passage to and from the cell. The interior apartment or cavity is about two inches deep, and is thickly lined with soft feathers; and the nest forms altogether a well-proportioned and symmetrical structure, testifying alike to the skill and industry of the modest little builder. The nest of the other species is of a somewhat similar size; but it is fuller in the middle than the one described, and is pear-shaped towards the apex instead of tapering. The materials composing it are of coarser texture, there is less execution or finish about it, and the ingenious porch, the peculiar feature of the one, is altogether wanting in the other.”
A specimen of the nest, with a porch entrance, in Dr. Sisson’s possession, measures nine inches, and is produced downwards to a point, instead of being rounded as in the typical examples.
* Having given the result of my own examination of the type of Gerggone igata, I think it is only right to quote, in full, the conclusion in an opposite direction arrived at by Mr. Sharpe, in his notes to the ‘Voyage of the Erebus and Terror,’ pp. 25, 26:—“During a recent visit to Paris I examined, in company with Dr. Oustalet, the type of this species, which still exists in the Jardin des Plantes…… We compared the type with Dr. Buller’s figure and with the specimens of Gerygone flaviventris and we could not believe that the two species were identical. I take the following observations from my note-book:—‘It is very close to G. flaviventris, but instead of being grey on the throat, the latter is whitish washed with yellow, a shade of which is also apparent on the cheeks; sides of the breast washed with brown; abdomen white, the flanks washed with yellow. “Wing 1·95 inch, tarsus ·75.’ The tail is imperfect, but on the feathers which remain the white spot is decidedly more correctly described as terminal instead of subterminal. I mention this latter observation á propos of the following remarks made by Dr. Buller in his great work: ‘In some examples the measurements are slightly larger, there is an absence of the yellow tinge on the abdomen, and the white spot on the lateral tail-feathers is terminal.’ The last-named author does not seem to allow these differences to be specific; but I think that further investigation by the field-observers in New Zealand may prove G. igata to be a good species, and I leave the matter in their hands.” On the other hand, Dr. Finsch, in a letter to myself, stated, as the result of an independent examination:—“It will interest you to hear that the specimen of the so-called Gerygone igata in the Museum at Paris is positively Gerygone flaviventris.”
As I have previously pointed out, in a communication to the Wellington Philosophical Society (November 12,1870), among the substances used as building-materials by this bird, spiders ‘nests are always conspicuous; indeed, in some specimens, the whole exterior surface is covered with them. The particular web chosen for this purpose is an adhesive cocoon of loose texture and of dull green colour. These spiders’ nests contain a cluster of flesh-coloured eggs or young; and in tearing them off the bird necessarily exposes the contents, which it eagerly devours. Thus, while engaged in collecting the requisite building-material, it finds also a plentiful supply of food—an economy of time and labour very necessary to a bird that requires to build a nest fully ten times its own size, and to rear the Cuckoo’s offspring in addition to its own. Curiously enough, the bird uses only the green-coloured nests of Epeira verrucosa, and rejects the orange-coloured nests of E. antipodiana. I think this may be explained on the principle of assimilative or protective colouring. Dry freshwater algæ are sometimes used for binding the exterior and giving additional firmness to the structure.
In the Canterbury Museum there is a beautiful nest of this species, composed almost wholly of sheeps ‘wool intermixed with soft dry leaves. It is almost globular in shape, with the entrance near the top, and is lightly suspended from a branch of Leptospermum. There is also another of much larger size, composed of wool and spiders’ nests, with fragments of cotton and twine carefully interwoven, and furnished with a hoodless vestibule or porch, composed of fibrous rootlets; the threshold is unusually deep and firm, probably because of the very yielding materials of which the nest is built.
Another series presents some curious departures from the normal type, showing that the exact form of the nest is often the result of accident, the structure being adapted to the materials of which it happens to be composed and to the circumstances of its location. The subjoined woodcuts may help to illustrate the subject. Fig. 1 represents a nest of larger size than usual, and of a long elliptical shape, which exhibits the uncommon feature of several soft Emu-feathers, worked into the felting among the other building-materials. Fig. 2 shows a nest of the ordinary form, ornamented with the long dry leaves of the red gum (Eucalyptus rostrata), around and among which the neat structure is most cleverly built. In fig. 3 there is a manifest departure from the typical character exhibited in fig. 4. Lastly, fig. 5 shows the condition of the nest after the young Cuckoo usurper has pulled it out of shape and symmetry. Four is the normal number of eggs, although there are sometimes six. They differ somewhat in size; and in shape are ovoido-conical or slightly pyriform. They are sometimes pure white, but more generally freckled and marked with purplish brown, and are so fragile in texture as to bear only the most delicate handling. Ordinary specimens measure ·7 of an inch in length by ·5 in breadth. I have remarked that among the highly variable eggs of this species several distinct types may be recognized, and that all the eggs in one nest are invariably alike. Thus there is the spotted variety, in which the whole surface is studded with scattered dots of purplish brown; secondly, the freckled variety, in which the coloration is more diffuse; and, thirdly, the zoned variety, presenting a broad zone of colour near the thick end. Two examples, taken from a nest which contained also an egg of the Shining Cuckoo, had the thick end broadly capped with reddish brown.