OCYDROME, a word formed from Ocydromus, meaning “swift-runner,” and suggested by J. Wagler in 1830 as a general term for the New Zealand bird called in the then unpublished manuscripts of J. R. Forster Rallus troglodytes, and so designated in 1788 by S. G. Gmelin, who knew of it through J. Latham’s English description. Wagler’s description has since been generally adopted, and the genus Ocydromus is accepted by most ornithologists as a valid group of Rallidae; but the number of species it contains is admittedly doubtful, owing to the variability in size and plumage which they exhibit, and their correct nomenclature must for the present be considered uncertain. Sir W. Buller in his Birds of New Zealand identifies the “Wood-hen,” observed in great abundance on the shores of Dusky Bay in 1773 by Cook and his companions on his second voyage, with the Gallirallus fuscus described and figured by Du Bus in 1847, and accordingly calls it O. fuscus; but it cannot be questioned that the species from this locality—which appears to have a somewhat limited range in the Middle Island, and never to be met with far from the sea-coast, where it lives wholly on crustaceans and other marine animals—is identical with that of the older authors just mentioned. In 1786 Sparrman, who had also been of Cook’s company, figured and described as Rallus australis a bird which, though said by him to be that of the southern coast of New Zealand, differs so much from the R. troglodytes as to compel a belief in its special distinctness; and indeed his species has generally been identified with the common “Weka” of the Maories of the Middle Island, which can scarcely be the case if his statement is absolutely true, since the latter does not appear to reach so far to the southward, or to affect the seashore. It may therefore be fairly inferred that his subject was obtained from some other locality. The North Island of New Zealand has what is allowed to be a third species, to which the name of Ocydromus earli is attached, and this was formerly very plentiful; but its numbers have rapidly decreased, and there is every chance of its soon being as extinct as is the species which tenanted Norfolk on its discovery by Cook in 1774, and which was doubtless distinct from all the rest, though no specimen of it is known to exist in any museum. Another species, O. sylvestris, smaller and lighter in colour than any of the rest, was found in 1869 to linger yet in Lord Howe's Island (Proc. Zool. Society, 1869, p. 473, pl. xxxv.). Somewhat differing from Ocydromus, but apparently very nearly allied to it, is a little bird peculiar, it is believed, to the Chatham Islands (Ibis, 1872, p. 247), and regarded by Captain Hutton as the type of a genus Cabalus under the name of C. modestus, while other naturalists consider it to be the young of the rare Rallus dieffenbachi. So far the distribution of the Ocydromine form is wholly in accordance with that of most others characteristic of the New Zealand sub-region; but a curious exception is asserted to have been found in the Gallirallus lafresnayanus of New Caledonia, which, though presenting some structural differences, has been referred to the genus Ocydromus.
The chief interest attaching to the Ocydromes is their inability to use in flight the wings with which they are furnished, and hence an extreme probability of the form becoming wholly extinct in a short time. Of this inability there are other instances among the Rallidae (see Moor-Hen); but here we have coupled with it the curious fact that in the skeleton the angle which the scapula makes with the coracoid is greater than a right angle, a peculiarity shared only, so far as is known, among the Carinatae by the dodo. The Ocydromes are birds of dull plumage, and mostly of retiring habits, though the common species is said to show great boldness towards man, and, from the accounts of Cook and the younger Forster, the birds seen by them displayed little fear. They are extremely destructive to eggs and to any other birds they can master. (A. N.)
- It also occurs in Stewart Island, and singularly enough on the more distant group known as the Snares. The Gallirallus brachypterus of Lafresnaye, of which the typical (and unique?) specimen from an unknown locality is in the Caen Museum, has also been referred to this species, but the propriety of the act may be doubted.
- The younger Forster remarked that the birds of Norfolk Island, though believed by the other naturalists of Cook's ship to be generally the same as those of New Zealand, were distinguished by their brighter colouring (see also Nestor). There can be no doubt that all the land-birds were specifically distinct. It is possible that Sparrman's R. australis, which cannot very confidently be referred to any known species of Ocydromus, may have been from Norfolk island.