Stephens Island wren  (Traversia lyalli)

Classified as Extinct (EX) on the IUCN Red List (1).

Now extinct, the Stephens Island wren was remarkable for being one of the few species of flightless, passerine birds (2) (3). Although distinctly wren-like in appearance, this species was not a member of the wren family, belonging instead to a more ancient family of tiny New Zealand birds, the Acanthisittidae (4). Like many other flightless birds, the Stephens Island wren had small, rounded wings, a short tail and soft, loose plumage (2). The upperparts were dark olive mottled with brown, with darker plumage on the wings and tail, while the throat and breast were olive-yellow becoming olive-brown on the underparts (4).

The Stephens Island wren was common throughout New Zealand until the introduction of the Pacific rat (Rattus exulans) around 1,000 years ago (5). By the time of the Europeans’ arrival in the early 19th century, it had become restricted to Stephens Island, where it probably survived until the mid to late 1890s (6).

The Stephens Island wren inhabited rocky areas amongst bush and forest (1) (6).

The few observations of the Stephens Island wren in the wild indicate that it was mostly active at night and only occasionally during the day. It was a nimble species, running swiftly amongst rocks, where, like related species that are still alive today, it probably foraged for small invertebrates (4).

Before the Europeans arrived in New Zealand, predation by the introduced Pacific rat (Rattus exulans) had already eliminated the Stephens Island wren from its entire habitat, with the exception of a small population on Stephens Island, which the rat had not colonised (5) (6). This population remained undisturbed until 1894, when a lighthouse was constructed on Stephens Island, leading to the clearance of a portion of the island’s bush and forest cover. While this was probably not a major factor in the decline of this species, the colonisation of the island also brought with it a non-native mammalian predator, the domestic cat. Various popular accounts have attributed the ultimate extinction of the Stephens Island wren to a single pet cat belonging to the lighthouse keeper but, in reality, it is likely that in the years following the construction of the lighthouse, a small, introduced population of cats exterminated the last remnants of this unique species (6).

While the extinction of the Stephens Island wren is a particularly striking example of the catastrophic effects that introduced species can have on native species (6), there are, unfortunately, a number of other native New Zealand species that have suffered a similar fate. In response to the threat of invasive species, the New Zealand government, along with various conservation organisations, have worked diligently to eradicate invasive mammals from New Zealand’s islands and to control invasive plant and animal species on the mainland, receiving international recognition for their efforts (7).

View information on this species at the UNEP World Conservation Monitoring Centre.

To learn more about invasive species management in New Zealand visit:

• Biosecurity in New Zealand:
  www.biosecurity.govt.nz
• Conservation International:
  www.biodiversityhotspots.org/xp/hotspots/new_zealand

For more information on this and other bird species please see:

• BirdLife International:
  http://www.birdlife.org