The Flightless Wren and the Lighthouse Cat
Extinct species are a fascination to most people — organisms which will never again be seen by man take on almost mythical properties, especially those which have no modern analogs. As might be expected, some tales of extinction have therefore grown prolific in the public mind, from the mass harvesting of passenger pigeons (Ectopistes migratorious) to the bounty hunting of Thylacines (Thylacinus cynecephalus). These eradications usually play out over decades and sometimes even centuries, but one remarkable story details an extinction in only a year in a tale involving a lighthouse keeper and a rampaging cat.
On a summer’s day in January 1894, a group of eager settlers arrive at their destination: Stephen’s Island, a plot of land off the Northern coast of South Island, New Zealand. The miniscule isle, only about the size Hyde Park, had proved a useful site for a recently constructed lighthouse and aided ships in navigating the trecherous Marlborough sounds. Seventeen pioneers set up a hamlet around the lighthouse. Included in this party was our protagonist, assistant lighthouse keeper David Lyall, and our other key player, a cat, widely referred to as ‘Tibbles’ (Though we could not find a legitimate source corroborating this name). We do not know whom, if anyone, this cat belonged to, but it inhabited the newly built settlement alongside the villagers. From time-to-time Tibbles would emerge from the dense hedges of the island interior bringing with her the bounties the day’s hunt, allowing David Lyall to confiscate the deceased or injured creatures. Lyall, an avid naturalist, was usually capable of identifying the numerous bird species dragged in by the cat, but every now and then Tibbles would present a puzzling bird, a tiny brown sort with stunted wings. Confused and undoubtedly intrigued by this bird, Lyall skinned several and sent (and in some cases sold) the specimens to ornithologists and collectors. The specimens belonged to a new species of New Zealand wren which was named Traversia lyalli in honour of David Lyall, as well as the primary collector Henry Travers who bought and resold most of the birds. Lyall noted that the wren, whilst never common, became increasingly scarce as the year went on, writing in the autumn of 1894 to Mr. Travers that he thought the population would disappear, and true enough, at the start of 1895 the assistant light housekeeper reported that he thought the species was no more. Supposedly, Tibbles was the perpetrator, having killed all the individuals of T. lyalli on the island in the span of a single year (1).
Fig 1. A male Lyall’s wren perches on a branch.
Terms of use: No Rights Reserved
In reality, the story is somewhat exaggerated. The wren had been offhandedly mentioned by workers constructing the lighthouse in 1892 (1), placing the date of discovery two years earlier. Furthermore, correspondence indicates that specimens may have been received by ornithologists as late as 1899, which implies that specimens were probably collected for a few years after Lyall’s reported disappearance (1). Nevertheless, even with a conservative estimate the discovery, description, and extinction of the Lyall’s wren all occurred within less than a decade. Another element of the tale which perhaps does not quite align with reality is the culprit. Tibbles alone probably can’t be held accountable for the demise of T. lyalli. Instead, it seems that the cat may have been pregnant upon arrival in 1894 and that a small population of young cats had formed by 1895 which would grow exponentially in the subsequent years. Additional cats being brought over can’t be precluded either. By 1897 the lighthousekeepers were outfitted with shotguns to kill some of the many feral cats and in 1901 a bounty was placed on any cat killed (1). Even so, some debate exists as to whether the cats were the primary cause of the extinction of Lyall’s wren, with alternative explanations such as habitat loss and excessive specimen collection. Habitat loss on Stephens Island certainly occurred, with most of the bush eventually being cleared, however such activities seem to have occurred post-extinction (1). As for specimens, only 15 are known to have been collected, which seems insufficient to warrant an extinction. Additionally, such specimens were either procured primarily or maybe even exclusively by Mr Lyall who claims to have obtained them secondhand from the cat (1). As such we can quite confidently lay the extinction of Traversia lyalli at the feet of Tibbles and her extended family. Unsurprisingly Lyall’s wren was not the only extinction that occurred on Stephen’s Island. Lyall himself notes that other birds such as the local saddlebacks (Philesturnus sp.) and the now extinct piopio (Turnagra sp.) started vanishing from the island around this time as well (1).
Though Lyall’s wren was discovered on Stephen’s Island and was only ever recorded alive at the locality, we actually have material attributed to the species from several sites on both the South and North Islands of New Zealand dating to the Late Pleistocene or Holocene (3, 6). Whilst we think of the Lyall’s wren as a 19th century extinction, it is more accurate to treat as the final straw. The extinction of this species from the mainland probably predates the European arrival (6). It’s curious to wonder if the Stephen’s Island population was the only one that lasted into the colonial era: after all the only reason we are fortunate enough to have historical accounts of Lyall’s wren is because of the interest in nature by Lyall, otherwise the rapid event would have gone unrecorded. Hypotheses for why the avifauna went extinct prior to western settlement tend to cluster around the arrival of the Maori in the 14th century and are usually attributed to hunting by humans (Homo sapiens), the polynesian rat (Rattus exulans) or habitat change caused by one of the aforementioned species (5), though that is a topic for another day. It is likely that the absence of either invader on Stephen’s Island is what allowed T. lyalli to linger for so long.
Fig 2. Location of Stephen’s Island and its lighthouse within New Zealand. The Lyall’s Wren is known from fossil remains from the two main islands of New Zealand but was only ever recorded live on Stephen’s Island.
So why is the extinction of the Stephen’s Island wren even significant? The species was quite remarkable, boasting both a unique ecology and evolution. Despite few eyewitness accounts from Lyall we know a fair bit of its lifestyle. Traversia lyalli had very reduced wings, suggesting it may have been flightless, and indeed an incredibly short keel reaffirms this (3), Lyall stated that the bird was never observed to fly, but instead would scuttle rapidly around the ground, much like a mouse (1). Whilst flightlessness itself is not unique in birds, it is incredibly rare in passerines (songbirds). In fact at the time of its discovery, Lyall’s wren was the only such bird known to exist. Since then, the related long-billed wren (Dendroscansor decurvirostris) and the Long-legged bunting (Emberia alcoveri) of Tnerife has also been shown to be flightless songbirds (4), but this conclusion was based on comparisons with the morphology of Lyall’s wren, demonstrating its importance as a reference of flightlessness. We are not certain what the diet of the wren was. Lyall describes the species as semi-nocturnal (1), which may be an anti-predatory response to the avian predators of New Zealand. This is corroborated by the fact that fossil remains are most commonly found in the middens of the extinct laughing owl (Ninox albifacies) (7). The species was slightly sexually dimorphic as well, with males exhibiting a yellow-brown plumage on the chest and neck (7). Traversia lyalli belongs to a family called the acanthisittidae, often called the New Zealand Wrens. This is however a misnomer, as they are not closely related to conventional wrens (Troglodytidae). In fact, the family is a sister group to all other passerines (2). Even amongst the acanthisittidae the Lyall’s wren is the most basal taxon, estimated to have diverged from all other New Zealand wrens during the Early Oligocene (2).
Fig 3. A male (Left) and female (right) Lyall’s Wren (Traversia lyalli). Males are distinguishable due to their bright yellow plumage on the chest and neck (7)
Terms of use: No Rights Reserved
Of equal import is what the Stephens islands wren represents. In a time where many native birds in New Zealand are extinct or hanging on by a thread due to the invasion of cats, weasels, and other introduced animals, Lyall’s wren appears the ultimate precautionary tale, a species wiped out by a single stowaway. Despite its hyperbole and misinformation, the story is both evocative and useful in the narrative of extinction and conservation. We let cats carelessly take over this island, but we can prevent it from happening on other wildlife refuges. One point, however, where the story falls short is it gives the impression that all was well with the wren prior to the arrival of the settlers and their feline companion. Nothing could be further from the truth; for the Lyall’s wren the European introduction of cats was simply the straw that broke the camel’s back and took out the last remnants of a species that had once been abundant throughout New Zealand.
Works Cited
1. 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, 193-200.
2. Michell, K. J., Wood, J. R., Llamas, B., McLenachan, P. A., Kardailsky, O., Scofield, R. P., Worthy, T. H., Cooper, A.. (2016). Molecular Phylogenetics and Evolution 102, 295-304.
3. Millener, P. R.. (1990). The only flightless passerine, the Stephens Island wren (Traversia lyalli: Acanthisittidae). Notornis 36(4), 280-284.
4. Rando, J. C., Lopez, M.. (1999). A new species of extinction flightless passerine (Emberizidae: Emberiza) from the Canary Islands. The Condor 101, 1-13.
5. Roff, D. A., Roff, R. J.. (2003). Of rats and Maoris: a novel method for the analysis of patterns of extinction in the New Zealand avifauna before European contact. Evolutionary Ecology Research 5, 759-779.
6. Worthy, T. H.. (1997). Quarternary fossil fauna of South Canterbury, South Island, New Zealand.
7. Southey, I. 2013. Lyall’s wren. In Miskelly, C.M. (ed.) New Zealand Birds Online. www.nzbirdsonline.org.nz
