Lyall's wren, the Stephens Island wren or the Stephens Island rockwren (Traversia lyalli) is an extinct species of small, flightless passerine bird belonging to the family Acanthisittidae, the New Zealand wrens. It was once found throughout New Zealand, but by the time of its discovery by scientists in 1894, it could only be found on Stephens Island in Cook Strait. Often claimed to be a species driven extinct by only a single individual animal (a lighthouse keeper's cat named Tibbles), it was actually predated upon by the numerous feral cats found throughout the island. The wren was described almost simultaneously by both Walter Rothschild and Walter Buller; it became extinct shortly thereafter.
Taxonomy The bird's scientific name commemorates the assistant lighthouse keeper, David Lyall, who first brought the bird to the attention of science. It was described as a distinct genus, Traversia, in honour of naturalist and curio dealer Henry H. Travers, who procured many specimens from Lyall. Traversia is a member of the family Acanthisittidae, or the New Zealand wrens – which are not wrens but a similar-looking lineage of passerines, originating in the Oligocene, and the sister group to all other songbirds. DNA analysis has confirmed that T. lyalli, the only member of its genus, is the oldest and most distinct lineage in the Acanthisittidae.
Description Lyall's wren had olive-brown plumage with a yellow stripe through the eye. Its underside was grey in females and brownish-yellow in males and its body feathers were edged with brown. Most distinctively, Lyall's wren was flightless, with a reduced keel on its breastbone and short rounded wings. It is the best known of the five flightless passerines (songbirds) known to science, all of which were inhabitants of islands and are now extinct. The others were three other New Zealand wrens (the long-billed wren and the two species of stout-legged wren) and the long-legged bunting from Tenerife, one of the Canary Islands, all of which were only recently discovered as fossils and became extinct in prehistoric times. Living Lyall's wrens were seen only twice. The lighthouse keeper described the 'rock wren', as he called it, as almost nocturnal, "running around the rocks like a mouse and so quick in its movements that he could not get near enough to hit it with a stick or stone".
Distribution
Historically, Lyall's wren was found only on Stephens Island. Prehistorically, it had been widespread throughout New Zealand before the land was settled by the Māori. Its bones can be found in caves and deposits left by laughing owls on both main islands. Its disappearance from the mainland was probably due to predation by the Polynesian rat or kiore (Rattus exulans), which had been introduced by the Māori. The presence of a flightless bird on an island 3.2 km from the mainland, along with Hamilton's frog (Leiopelma hamiltoni), which can be killed by exposure to salt water, may seem puzzling, but Stephens Island was connected to the rest of New Zealand during the last glaciation when sea levels were lower.
Extinction
Much of what is commonly assumed to be established knowledge about this species' extinction is either wrong or has been misinterpreted, starting with the account by Rothschild (1905) who claimed that a single cat had killed all of the birds. The research of Galbreath and Brown (2004) and Medway (2004) has uncovered much of the actual history of the bird during the short time that it was known to researchers, and concluded that the extinction of the bird was caused by hunting from an established population of feral cats, rather than from a single individual, and that it occurred over a period of a few years rather than over a single year as commonly recounted. Additional causes for the species' decline, such as hunting by human collectors and the clearing of native brush for construction, have also been debated.
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