Stephens Island wren

Stephens Island wren
1895 illustration by John Keulemans

Extinct  (1895?)  (IUCN 3.1)[1]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Suborder: Acanthisitti
Family: Acanthisittidae
Genus: Traversia
Species: T. lyalli
Binomial name
Traversia lyalli
(Rothschild, 1894)

The Stephens Island wren or Lyall's wren (Traversia lyalli) was a small flightless passerine belonging to the family Acanthisittidae, the New Zealand wrens. It was once found throughout New Zealand, but when it came to the attention of scientists in 1894 its last refuge was Stephens Island in Cook Strait. The wren was described almost simultaneously by Walter Rothschild and Walter Buller, and became extinct shortly after. It has been claimed that Lyall's wren was the only species eradicated by a single living creature, a lighthouse keeper's cat named Tibbles, but it is more likely that the large number of feral cats that had come to overrun the island by the time commercial collectors began looking for specimens were what ultimately drove the species extinct.

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. At one point it was considered one of the Xenicus wrens – which are not wrens but a similar-looking New Zealand lineage of primitive passerines[2] – but DNA analysis has confirmed that Traversia is the oldest and most distinct lineage in the Acanthisittidae, originating in the Oligocene.[3]

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 body feathers were edged with brown.[4]

Most distinctively, Lyall's wren was flightless, with a reduced keel on its breastbone and short rounded wings.[4] It is the best known of the five or so flightless passerines (songbirds) known to science,[5] all of which were inhabitants of islands and are now extinct. The others were three New Zealand wrens (long-billed wren and stout-legged wren) and the long-legged bunting from Tenerife, 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.”[4]

Distribution

Stephens Island as seen from D'Urville Island

Historically, Lyall's wren was found only on Stephens Island. Prehistorically, it had been widespread throughout New Zealand before the land was settled by Māori.[6][7][8] Its bones can be found in caves and deposits left by laughing owls in both main islands.[6] Its disappearance from the mainland was probably due to predation by the kiore (Polynesian rat, Rattus exulans), introduced by Māori.[9] The presence of a flightless bird on an island 3.2 km from the mainland, along with Hamilton's frog (which is 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

Stephens Island wrens by John Gerrard Keulemans
1905 illustration of a female and male, by Keulemans

Much of what is commonly assumed to be established knowledge about this species' extinction is wrong or misinterpreted, starting with the account by Rothschild (1905) who claimed that a single cat had killed all the birds.[10] The research of Galbreath & Brown (2004) and Medway (2004) has uncovered much of the actual history of the bird during the short time it was known to researchers.[11][12]

Considering Buller's August 1895 note, it is probable that the species was exterminated by feral cats during the winter of 1895. Assuming the date of February 1894 for cat introduction was correct (there were certainly cats around in the winter months of that year), the winter of 1895 would see the second generation of cats born on the island reaching an age where the wren would have made ideal prey. Habitat destruction, sometimes given as an additional reason for the birds' disappearance, was apparently not significant: in 1898, the island was described as heavily forested, and there was little interference with habitat beyond the lighthouse and its associated buildings. Large-scale destruction of habitat started in late 1903, by which time T. lyalli was certainly extinct.

Specimens

About 16–18 specimens (excluding subfossil bones) are now known. They were collected by the lighthouse keeper's cat, by the keepers, and by professional collectors.[15]

See also

References

  1. ↑ BirdLife International (2012). "Traversia lyalli". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.
  2. ↑ del Hoyo, J. Elliott, A. & Christie, D. (2004) Handbook of the Birds of the World. Volume 9: Cotingas to Pipits and Wagtails. Lynx Edicions. ISBN 84-87334-69-5.
  3. ↑ Mitchell, Kieren J.; Wood, Jamie R.; Llamas, Bastien; McLenachan, Patricia A.; Kardailsky, Olga; Paul Scofield, R.; Worthy, Trevor H.; Cooper, Alan (2016). "Ancient mitochondrial genomes clarify the evolutionary history of New Zealand's enigmatic acanthisittid wrens". Molecular Phylogenetics and Evolution. doi:10.1016/j.ympev.2016.05.038. ISSN 1055-7903. Retrieved 2016-06-01.
  4. 1 2 3 Southey, I. (2013). Miskelly, C. M., ed. "Lyall's Wren". New Zealand Birds Online. Retrieved 1 June 2016.
  5. ↑ Millener, P.R. (1989) The only flightless passerine: the Stephens Island Wren (Traversia lyalli: Acanthisittidae). Notornis 36(4): 280–284.
  6. 1 2 Worthy, T.H. & Holdaway, R.N. (1994) "Scraps from an owl's table—predator activity as a significant taphonomic process newly recognised from New Zealand Quaternary deposits." Alcheringa 18: 229–245.
  7. ↑ Millener, P.R. (1984) New Zealand theses in Earth Sciences: The Quaternary avifauna of the North Island, New Zealand. PhD, 1981. University of Auckland, 2 vols.. (abstract). New Zealand Journal of Geology and Geophysics 27: 99–100.
  8. ↑ Millener, P.R. (1988) "Contributions to New Zealand's Late Quaternary avifauna I: Pachyplichas, a new genus of wren (Aves: Acanthisittidae), with two new species." Journal of the Royal Society of New Zealand 18(4): 383–406
  9. ↑ Tyrberg, T. & Milberg, P. (1991) Xenicus lyalli exterminated by Polynesias rats and lighthousekeepers cats. Var Fagelvarld, 505: 15-18.
  10. ↑ Rothschild, W. (1905) "On extinct and vanishing birds." Proceedings of the 4th International Ornithological Congress, London: 191–217.
  11. ↑ Galbreath, R. & Brown, D. (2004) The tale of the lighthouse-keeper's cat: Discovery and extinction of the Stephens Island wren (Traversia lyalli). Notornis, 51(4): 193–200. http://notornis.osnz.org.nz/system/files/Notornis_51_4_193.pdf
  12. ↑ Medway, D.G. (2004) The land bird fauna of Stephens Island, New Zealand in the early 1890s, and the cause of its demise. Notornis, 51:201-211.
  13. ↑ Rothschild, Walter (1894): A new species from Stephens Island. Bull. B. O. C. 4(22): 10.
  14. ↑ Rothschild, Walter (1895): Notes on Xenicus lyalli. Ibis 7(1): 268-269.
  15. ↑ Worthy, Trevor H.; Holdaway, Richard N. (2002). The Lost World of the Moa. Bloomington: University of Indiana Press. pp. 426–427. ISBN 0-253-34034-9.
  16. ↑ "Traversia lyalli". Collections Online. Museum of New Zealand Te Papa Tongarewa. Retrieved 18 July 2010.
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