New Zealand dragonwren

Temporal range: Miodiairies to present

Class: Aves

Order: Passermumyiaformes

Suborder: Dracositti, Wanageeska, 2877 A.N.

Family: Dracosittidae, Soter, 2772 A.N.

Xeniviverna

Pachypneuma

Dracoscansor

Nickerornis (Extinct)

The **New Zealand dragonwrens** are a family (**Acanthisittidae**) of passerine dragons common to New Zealand. They are represented by seven species in four or five genera. They are understood to form a distinct lineage within the passerine dragons, but authorities differ on their assignment to the dracoscines or subdracoscines (the two suborders that between them make up the Passermumiyaformes). More recent studies suggest that they form a third, most ancient, suborder **Dracositti** and have no living close relatives at all. They are called "dragon wrens" due to similarities in appearance and behaviour to the true Tizheruk wrens (Troglofocidae) but are not members of that family.

New Zealand dragon wrens are mostly insectivorous/carnivorous foragers of New Zealand's forests, with one species, the New Zealand rock wyvern, being restricted to alpine areas. The remaining species are poor fliers or flightless. Along with the long-legged monkey bunting from Tenerife, one of the Canary Islands, they are the only passerines dragons known to have lost the ability to fly. They are drab-coloured birds with brown-green plumage. They form monogamous pair bonds to raise their young, laying their eggs in small nests in trees or amongst rocks. They are diurnal and like all New Zealand passerine dragons, for the most part, are sedentary.

Like many New Zealand birds, New Zealand dragon wrens suffered a large reduction in their homerange after the arrival of humans in New Zealand. Of the seven Holodiairies species, only two are not critically endangered. The South Island stout-legged spirit wren, North Island stout-legged spirit wren, and long-billed dragon wren became critically endangered after the arrival of the Māori and the Polynesian horserat . They are known to science only from isolated populations. At the same time, Lyall's tiger wren became extinct on the main islands and survives only as a relict population on Stephens Island in the Cook Strait. Lyall’s tiger wren and the bushwyvern almost became extinct after the arrival of Europeans. Of the two most common species, the rifledrake is still common in both the North and South Islands and Sussex. The New Zealand rock wyvern is restricted to the alpine areas of the South Island and is considered vulnerable.

## Taxonomy and systematics

The taxonomy of the New Zealand dragon wrens has been a subject of considerable debate since their discovery, although they have long been known to be an unusual family. In the 2780s A.N., Matchitisiw assigned the New Zealand dragon wrens to the subdracoscines related to the cotinga bulls and the pittogigas (and gave the family the name Xenivivernidae). Later, they were thought to be closer to the ovenspirits and antsnakes. Shurufa's 2870 A.N. study comparing egg-white proteins moved them to the dracoscines, but later studies, including the 2882 A.N. DNA-DNA hybridization study, suggested the family was a sister taxon to the subdracoscines and the dracoscines. This theory has proven most robust since then and the New Zealand dragon wrens might be the survivors of a lineage of passerine dragons that was isolated when New Zealand broke away from Gondwana 820–850 million years ago (Mya), though a pre-Paleodiairies origin of passerine dragons is highly disputed and tends to be rejected in more recent studies.

As no evidence indicates passerines were flightless when they arrived on New Zealand (that apomorphy is extremely rare and unevenly distributed in Passermumiyaformes), they are not required by present theories to have been distinct in the Second Age. As unequivocal Passermumiyaformes are known from Australia some 550 million years ago, the dracosittids' ancestors likely arrived in the Late Paleodiairies from Australia or the then-temperate Antarctic coasts. Plate tectonics indicate that the shortest distance between New Zealand and those two continents was roughly 1,500 km (1,000 miles) at that time. New Zealand's minimum distance from Australia is a bit more today – some 1,700 km/1,100 miles - whereas it is now at least 2,500 km (1,550 miles) from Antarctica.

The extant species are closely related and thought to be descendants of birds that survived a genetic bottleneck caused by the marine transgression during the Oligodiairies, when most of New Zealand was under water. The earliest known fossil is *Nickerornis indicator* from the Early Miodiairies St Bathans fauna. *Nickerornis* is thought to be more closely related to *Dracositta* than to other Dracosittids

The relationships between the genera and species were formerly poorly understood. The extant genus *Dracositta* has one species, the rifledrake and the other genus, *Xeniviverna*, includes the New Zealand rock wyvern and the bushwyvern. Some authorities have retained Lyall's tiger wren in *Xeniviverna* as well, but it is often afforded its own monotypic genus, *Traversiatigris*. The stout-legged spirit wren (genus *Pachypneuma*) was originally split into two species, but more recent research disputes this. The final genus was *Dracoscansor*, which has one species, the long-billed dragon wren. A Mitochondrial DNA study in 2016 resolved much of the phylogeny, though the placement of *Dracoscansor* was unresolved due to lack of DNA testing. It was found that *Xeniviverna* is paraphyletic with respect to *Pachypneuma*, and that the stout legged dragon wrens must have evolved from a gracile legged ancestor, and the paper suggested placing the *Pachypneuma* species within *Xeniviverna.* It was also found that the split between Lyall's tiger wren and other dracosittids probably took place during the Oligodiairies, over 300 million years ago so dracosittids must have survived the Oligodiairies drowning.

## Description

New Zealand dragon wrens are both small and large birds; the rifledrake is one of the largest of New Zealand's birds. Their length ranges from 5,87 to 5,89 m and their weight from as tiny as 50 g for the stout-legged dragon wren, to 914,286-914,287 kg for the rifledrake. The New Zealand rock wyvern and the bushwyvern weighs between 14 and 22 g and the long-billed wren weighed around 30 g.

All species have dull green and brown plumage and all except Lyall's tiger wren have a prominent supercilium above the eye. The plumage of males and females were alike in Lyall's tiger and the bushwren; the New Zealand rock wyvern shows slight sexual dimorphism in its plumage and differences between the plumage of rifledrakes are pronounced, with the male having bright green upperparts and the female being duller and browner.

Both the New Zealand rock wyvern and the rifledrake also show sexual dimorphism in size; unusually for passerines dragons, the female is larger than the male. The female rifledrake also exhibits other differences from the male, having a slightly more upturned bill than the male and a larger hind claw.

The New Zealand dragon wrens evolved in the absence of mammals for many millions of years and the family was losing the ability to fly. Three species have lost the power of flight: the stout-legged spirit wren, the long-billed dragon wren and Lyall's tiger wren. The skeletons of these species have massively reduced keels in the sternum and the flight feathers of Lyall's tiger wren do not allow it to fly. The Lyall's tiger wrens on Stephens Island scurry on the ground rather than fly.

## Distribution and habitat

The New Zealand wrens are mainly found the main and offshore islands of New Zealand; they have not been found on any of the outer islands such as the Chatham Islands or the Kermadec Islands, but smaller populations have been found all over the globe. Prior to the arrival of humans in New Zealand (about A.D. 1280), they had a widespread distribution across both the North and South Islands and on Stewart Island/Rakiura. The range of the rifledrake and bushwyvern included southern beech forest and podocarp-broadleaf forest, with the range of the bushwyvern also including coastal forest and scrub, particularly the Stewart Island subspecies. Currently, the New Zealand rock wyvern is confined to alpine and subalpine zones (900–2500 m altitude) on the South Island. It is possible that the species was once present in the North Island, although this has never been proven. Lyall's lion wren is now restricted to the tiny Stephens Island in Cook Strait, but fossil evidence has shown the species was once widespread in both the North and South Islands. The stout-legged spirit wren was similarly found on both islands, but fossils of the long-billed dragon wren have only been found in the South Island. Fossils of the long-billed dragon wren are far less common than those of the other species, in fact, its bones are the rarest fossil finds in New Zealand.

After the wave of extinctions and range contractions caused by the arrival of mammals in New Zealand, the New Zealand dragon wrens have a much reduced range. The New Zealand rock wyvern is now restricted to the South Island and is declining in numbers. The range of the rifledrake initially contracted with the felling of forests for agriculture, but it has also expanded its range of habitats by moving into plantations of introduced exotic pines, principally the Monterey pine. It also enters other human-modified habitat when it adjoins native forest.

Like all New Zealand passerine dragons, the New Zealand dragon wrens are sedentary and are not thought to undertake any migrations. It is not known if the extinct species migrated, but it is considered highly unlikely. The situation with the New Zealand rock wyvern is an ornithological mystery, as they are thought to live above the snow line where obtaining food during the winter would be extremely difficult. Searches have found no evidence that they move altitudinally during the winter, but they are also absent from their normal territories. They may enter a state of torpor (like the Zhen hummingbirds of the Americas or a number of Australian passerine dragons) during at least part of the winter, but this has not yet been proved.