1902 Encyclopedia > Zosterops

Zosterops




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ZOSTEROPS, originally the scientific name of a genus of birds founded by Vigors and Horsfield (Tram. Linn. Society, xv. p. 235) on an Australian species called by them Z. dorsalis, but subsequently shown to be identical with the Certhia cxrulescens, and also with the Sylvia lateralis, previously described by Latham. Latterly the name has been. Anglicized in the same sense, and, whether as a scientific or a vernacular term, applied to a great number of species of little birds which inhabit for the most part the tropical districts of the Old World, from Africa to most of the islands in the Indian and Pacific Oceans, and northwards in Asia through India and China to Amurland and Japan.
The birds of this group are mostly of unpretending appearance, the plumage above being generally either mouse-coloured or greenish olive ; but some are sufficiently varied by the white or bright yellow of their throat, breast, or lower parts, and several have the flanks of a more or less lively bay. It is remarkable that several islands are inhabited by two perfectly distinct species, one belonging to the brown and the other to the green section, the former being wholly insular. The greater number of spiecies seem to be confined to single islands, often of very small area, but others have a very wide dis-tribution, and much interest has been excited by the undoubted fact that the type-species, Z. cserulescens, has of late years largely ex-tended its range. First described from New South Wales, wdiere it is very plentiful, it had been long known to inhabit all the eastern part of Australia. In 1856 it was noticed by naturalists as occur-ring in the South Island of New Zealand, when it became known to the Maories by a name signifying " Stranger," and to the English settlers as the "Blight-bird," from its clearing the fruit-trees of a blight by which they had lately been affected. It soon after-appeared in the North Island, wdiere it speedily became common, and it has thence not only spread to the Chatham Islands, but, as Sir Walter Buller states (Birds N. Zealand, ed. 2, i. p. 79), it has been met with in considerable numbers 300 miles from land, as though in search of new countries to colonize. Yet this author be-lieves it to be indigenous to the west coast of the South Island, and Sir James Hector joins in that opinion. If they be right, it is, however, piretty certain that until the year before mentioned it must have been confined to an extremely small district, and the only assignable cause of its spreading so rapidly, when it did extend its range, is that of a large surplus population unable to find a living at home. It is known to propagate at a high rate of increase, and at times numbers have been found dead, apparently for want of food. In any case it is obvious that this Zosterops must be a compara-tively modern settler in New Zealand.
All the species of Zosterops are sociable, consorting in large flocks, which only separate on the aprproach of the piairing season. They build nests, described as being variously placed—sometimes suspended from a horizontal fork and sometimes fixed in an upright crotch—and lay (so far as is known) pale blue, spotless eggs, thereby differing wholly from several of the groups of birds to which they have been thought allied. Though mainly insectivorous, the birds of this genus will eat fruits of various kinds and in such quantities as to be at times injurious. The habits of Z. cxrulescens havp been well described by Sir W. Buller (ut supra.), and those of s species peculiar to Ceylon, Z. ceylonensis, by Col. Legge (B. Ceyljn, p. 586), while those of the widely-ranging Indian Z. palpebrora and of the South-African Z. capensis have been succinctly treated by Jerdon (B. India, ii. p. 266) and Mr Layard (B. South Africa, p. 116) re-spectively.
It is a remarkable and, if capable of explanation, would doubtless be an instructive fact that the largest known spiecies of the genus, Z. albigularis, measuring nearly 6 inches in length, is confined to so small a spot as Norfolk Island, where also another, Z. tcnui-rostris, not much less in size, occurs ; while a third, of intermediate stature, Z. strenua, inhabits the still smaller Lord Howe's Island. A fourth, Z. vatensis, but little inferior in bulk, is found on one of the New Hebrides ; but, after these giants of their kind, the rest fall off considerably, being from one-fifth to one-third less in length, and some of the smaller species hardly exceed 8J inches from end to end.
The affinities of the genus Zosterops are by no means clear. Placed by some writers, if not systematists, with the Paridx (cf. TITMOUSE), by others among the Meli-_pliagidx (cf. HONEY-EATER), and again by others with the Nectariniidx (cf. SUNBIRD), the structure of the tongue, as shown by Dr Gadow (Proc. Zool. Society, 1883, pp. 63, 68, pi. xvi. fig. 2), entirely removes it from the first and third, and from most of the forms generally included among the second. On the whole it seems safest to regard the genus, at least provisionally, as the type of a distinct
Family.—Zosteropidx—as Families go among Passerine birds; but, whether the Australian genera Melithreptus and Plectrorhamphus (otherwise Plectrorhyncha) should be included under that heading, as has been done, remains to be proved, and in the meanwhile may be reasonably doubted. (A. N.)








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