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 species seem to be confined to single islands, often of very small area, but others have a very wide distribution, and much interest has been excited by the undoubted fact that the type-species, Z. caerulescens, has of late years largely extended its range. First described from New South Wales, where 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 occurring 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, where 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 believes 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, pretty 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 comparatively modern settler in New Zealand.