Acanthisittidae
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The New Zealand wrens are a
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
(Acanthisittidae) of tiny
passerine A passerine () is any bird of the order Passeriformes (; from Latin 'sparrow' and '-shaped') which includes more than half of all bird species. Sometimes known as perching birds, passerines generally have an anisodactyl arrangement of their ...
s
endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
to
New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...
. They were represented by seven
Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
in four or five
genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...
, although only two species in two genera survive today. They are understood to form a distinct lineage within the passerines, but authorities differ on their assignment to the oscines or suboscines (the two suborders that between them make up the Passeriformes). More recent studies suggest that they form a third, most ancient, suborder Acanthisitti and have no living close relatives at all. They are called "wrens" because of similarities in appearance and behaviour to the true
wren Wrens are a family, Troglodytidae, of small brown passerine birds. The family includes 96 species and is divided into 19 genera. All species are restricted to the New World except for the Eurasian wren that is widely distributed in the Old Worl ...
s (Troglodytidae) but are not members of that family. New Zealand wrens are mostly insectivorous foragers of New Zealand's forests, with one species, the New Zealand rock wren, being restricted to alpine areas. Both the remaining species are poor fliers and four of the five extinct species are known or suspected to have been flightless. Along with the long-legged bunting from
Tenerife Tenerife ( ; ; formerly spelled ''Teneriffe'') is the largest and most populous island of the Canary Islands, an Autonomous communities of Spain, autonomous community of Spain. With a land area of and a population of 965,575 inhabitants as of A ...
, one of the
Canary Islands The Canary Islands (; ) or Canaries are an archipelago in the Atlantic Ocean and the southernmost Autonomous communities of Spain, Autonomous Community of Spain. They are located in the northwest of Africa, with the closest point to the cont ...
, they are the only passerines known to have lost the ability to fly. Of the species for which the
plumage Plumage () is a layer of feathers that covers a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, there can b ...
is known, they are drab-coloured birds with brown-green plumage. They form
monogamous Monogamy ( ) is a relationship of two individuals in which they form a mutual and exclusive intimate partnership. Having only one partner at any one time, whether for life or serial monogamy, contrasts with various forms of non-monogamy (e.g. ...
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 passerines, are, for the most part, sedentary. Like many New Zealand birds, New Zealand wrens suffered several
extinction Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
s after the arrival of humans in New Zealand. Of the seven
Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...
species, only two survive today. The South Island stout-legged wren, North Island stout-legged wren, and long-billed wren became extinct after the arrival of the Māori and the
Polynesian rat The Polynesian rat, Pacific rat or little rat (''Rattus exulans''), or , is the third most widespread species of rat in the world behind the brown rat and black rat. Contrary to its vernacular name, the Polynesian rat originated in Southeast Asi ...
. They are known to science only from
subfossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
remains. At the same time, Lyall's wren became extinct on the main islands and survived only as a relict population on Stephens Island in the
Cook Strait Cook Strait () is a strait that separates the North Island, North and South Islands of New Zealand. The strait connects the Tasman Sea on the northwest with the South Pacific Ocean on the southeast. It is wide at its narrowest point,McLintock, ...
. Lyall's wren and the bushwren became extinct after the arrival of Europeans in 1895 and 1972 respectively. Of the two remaining species, the
rifleman A rifleman is an infantry soldier armed with a rifling, rifled long gun. Although the rifleman role had its origin with 16th century hand cannoneers and 17th century musketeers, the term originated in the 18th century with the introduction o ...
is still common in both the North and South Islands. The New Zealand rock wren is restricted to the alpine areas of the South Island and is considered vulnerable.


Taxonomy and systematics

The taxonomy of the New Zealand wrens has been a subject of considerable debate since their discovery, although they have long been known to be an unusual family. In the 1880s,
Forbes ''Forbes'' () is an American business magazine founded by B. C. Forbes in 1917. It has been owned by the Hong Kong–based investment group Integrated Whale Media Investments since 2014. Its chairman and editor-in-chief is Steve Forbes. The co ...
assigned the New Zealand wrens to the suboscines related to the cotingas and the pittas (and gave the family the name Xenicidae). Later, they were thought to be closer to the
ovenbird The ovenbird (''Seiurus aurocapilla'') is a small songbird of the New World warbler family (biology), family (Parulidae). This bird migration, migratory bird breeds in eastern North America and winters in Central America, many List of Caribbean ...
s and antbirds. Sibley's 1970 study comparing egg-white
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
s moved them to the oscines, but later studies, including the 1982 DNA-DNA hybridization study, suggested the family was a sister taxon to the suboscines and the oscines. This theory has proven most robust since then and the New Zealand wrens might be the survivors of a lineage of passerines that was isolated when New Zealand broke away from
Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...
82–85
million years ago Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...
(Mya), though a pre-
Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...
origin of passerines 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
apomorph In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to ha ...
y is extremely rare and unevenly distributed in Passeriformes), they are not required by present theories to have been distinct in the
Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...
. As unequivocal Passeriformes are known from
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
some 55 million years ago, the acanthisittids' ancestors likely arrived in the
Late Paleocene The Thanetian is, in the International Commission on Stratigraphy, ICS Geologic timescale, the latest age (geology), age or uppermost stage (stratigraphy), stratigraphic stage of the Paleocene epoch (geology), Epoch or series (stratigraphy), Serie ...
from Australia or the then-
temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...
Antarctic The Antarctic (, ; commonly ) is the polar regions of Earth, polar region of Earth that surrounds the South Pole, lying within the Antarctic Circle. It is antipodes, diametrically opposite of the Arctic region around the North Pole. The Antar ...
coasts.
Plate tectonics Plate tectonics (, ) is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of , an idea developed durin ...
indicate that the shortest distance between New Zealand and those two continents was roughly at that time. New Zealand's minimum distance from Australia is a bit more today – some – whereas it is now at least 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 A marine transgression is a geologic event where sea level rises relative to the land and the shoreline moves toward higher ground, resulting in flooding. Transgressions can be caused by the land sinking or by the ocean basins filling with water ...
during the
Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
, when most of New Zealand was under water. The earliest known fossil is '' Kuiornis indicator'' from the
Early Miocene The Early Miocene (also known as Lower Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages: the Aquitanian age, Aquitanian and Burdigalian stages. The sub-epoch lasted from 23.03 ± 0.05 annum, Ma to ...
St Bathans fauna. ''Kuiornis'' is thought to be more closely related to ''Acanthisitta'' than to other Acanthisittids. The relationships between genera and species were formerly poorly understood. The extant genus ''Acanthisitta'' has one species, the
rifleman A rifleman is an infantry soldier armed with a rifling, rifled long gun. Although the rifleman role had its origin with 16th century hand cannoneers and 17th century musketeers, the term originated in the 18th century with the introduction o ...
, and the other surviving genus, ''Xenicus'', includes the New Zealand rock wren and the recently extinct bushwren. Some authorities have retained Lyall's wren in ''Xenicus'' as well, but it is often afforded its own monotypic genus, ''Traversia''. The stout-legged wren (genus ''Pachyplichas'') was originally split into two species, but more recent research disputes this. The final genus was ''Dendroscansor'', which had one species, the long-billed wren. A mitochondrial DNA study in 2016 resolved much of the phylogeny, though the placement of ''Dendroscansor'' was unresolved due to lack of DNA testing due to the rarity of its remains. It was found that ''Xenicus'' was
paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...
with respect to ''Pachyplichas'', and that the stout legged wrens must have evolved from a gracile-legged ancestor, and the paper suggested placing the ''Pachyplichas'' species within ''Xenicus.'' It was also found that the split between Lyall's wren and other acanthisittids probably took place during the Oligocene, over 30 million years ago, so acanthisittids must have survived the Oligocene drowning. A
cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
is given below:


Recent genera and species

*Genus †''Traversia'' ** † Lyall's wren, ''Traversia lyalli'' *Genus ''Acanthisitta'' **
Rifleman A rifleman is an infantry soldier armed with a rifling, rifled long gun. Although the rifleman role had its origin with 16th century hand cannoneers and 17th century musketeers, the term originated in the 18th century with the introduction o ...
, ''Acanthisitta chloris'' *Genus '' Xenicus'' ** † Bushwren, ''Xenicus longipes'' ** New Zealand rock wren, ''Xenicus gilviventris'' ** † North Island stout-legged wren, ''Xenicus jagmi'' (possibly conspecific with ''Xenicus yaldwyni'') ** † South Island stout-legged wren, ''Xenicus yaldwyni'' *Genus †'' Dendroscansor'' ** † Long-billed wren (New Zealand), ''Dendroscansor decurvirostris''


Fossil genus and species

†'' Kuiornis indicator'' from the
Early Miocene The Early Miocene (also known as Lower Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages: the Aquitanian age, Aquitanian and Burdigalian stages. The sub-epoch lasted from 23.03 ± 0.05 annum, Ma to ...
St Bathans fauna


Description

New Zealand wrens are tiny birds; the rifleman is the smallest of New Zealand's birds. Their length ranges from 7 to 10 cm and their weight ranges from as little as 5–7 g for the rifleman, to an estimated 50 g for the extinct stout-legged wren. The New Zealand rock wren (and probably the bushwren) weighs between 14 and 22 g and the extinct long-billed wren weighed around 30 g. The
plumage Plumage () is a layer of feathers that covers a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, there can b ...
of the New Zealand wrens is only known for the four species seen by European scientists. All these species have dull green and brown plumage and all except Lyall's wren have a prominent supercilium above the eye. The plumage of males and females were alike in Lyall's wren and the bushwren; the New Zealand rock wren shows slight
sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...
in its plumage and differences between the plumage of riflemen are pronounced, with the male having bright green upperparts and the female being duller and browner. Both the New Zealand rock wren and the rifleman also show sexual dimorphism in size; unusually for
passerine A passerine () is any bird of the order Passeriformes (; from Latin 'sparrow' and '-shaped') which includes more than half of all bird species. Sometimes known as perching birds, passerines generally have an anisodactyl arrangement of their ...
s, the female is larger than the male. The female rifleman also exhibits other differences from the male, having a slightly more upturned bill than the male and a larger hind
claw A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or Arthro ...
. The New Zealand wrens evolved in the absence of mammals for many millions of years and the family was losing the ability to fly. Three species are thought to have lost the power of flight: the stout-legged wren, the long-billed wren and Lyall's wren. The
skeleton A skeleton is the structural frame that supports the body of most animals. There are several types of skeletons, including the exoskeleton, which is a rigid outer shell that holds up an organism's shape; the endoskeleton, a rigid internal fra ...
s of these species have massively reduced keels in the
sternum The sternum (: sternums or sterna) or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major bl ...
and the flight
feather Feathers are epidermal growths that form a distinctive outer covering, or plumage, on both avian (bird) and some non-avian dinosaurs and other archosaurs. They are the most complex integumentary structures found in vertebrates and an exa ...
s of Lyall's wren also indicate flightlessness. Contemporary accounts of the Lyall's wrens on Stephens Island describe the species as scurrying on the ground rather than flying.


Distribution and habitat

The New Zealand wrens are
endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
and restricted to the main and offshore islands of New Zealand; they have not been found on any of the outer islands such as the
Chatham Islands The Chatham Islands ( ; Moriori language, Moriori: , 'Misty Sun'; ) are an archipelago in the Pacific Ocean about east of New Zealand's South Island, administered as part of New Zealand, and consisting of about 10 islands within an approxima ...
or the Kermadec Islands. Prior to the arrival of humans in New Zealand (about 1280 CE), they had a widespread distribution across both the North and South Islands and on Stewart Island. The range of the rifleman and bushwren included southern beech forest and podocarp-broadleaf forest, with the range of the bushwren also including coastal forest and scrub, particularly the Stewart Island subspecies. Currently, the New Zealand rock wren 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 wren was once thought to have been restricted to the tiny Stephens Island in Cook Strait,Fuller, E. (2002). Foreword; Extinct Birds pp.11–69 in del Hoyo J., Elliott A. & Christie D.A. (2004). ''Handbook of the Birds of the World. Volume 7. Jamacars to Woodpeckers.'' Barcelona:Lynx Edicions. but fossil evidence has shown the species was once widespread in both the North and South Islands. The stout-legged wren was similarly found on both islands, but fossils of the long-billed wren have only been found in the South Island. Fossils of the long-billed 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 wrens have a much reduced range. The New Zealand rock wren is now restricted to the South Island and is declining in numbers. The range of the rifleman initially contracted with the felling of forests for agriculture, but it has also expanded its range of habitats by moving into
plantation Plantations are farms specializing in cash crops, usually mainly planting a single crop, with perhaps ancillary areas for vegetables for eating and so on. Plantations, centered on a plantation house, grow crops including cotton, cannabis, tob ...
s of introduced exotic
pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. ''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as cu ...
s, principally the
Monterey pine ''Pinus radiata'' (synonym (taxonomy), syn. ''Pinus insignis''), the Monterey pine, insignis pine or radiata pine, is a species of pine native to the Central Coast (California), Central Coast of California and Mexico (on Guadalupe Island and Ced ...
. It also enters other human-modified habitat when it adjoins native forest. Like all New Zealand passerines, the New Zealand 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, as three of the extinct species were flightless. The situation with the New Zealand rock wren 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 Torpor is a state of decreased physiological activity in an animal, usually marked by a reduced body temperature and metabolic rate. Torpor enables animals to survive periods of reduced food availability. The term "torpor" can refer to the ti ...
(like the
hummingbird Hummingbirds are birds native to the Americas and comprise the Family (biology), biological family Trochilidae. With approximately 366 species and 113 genus, genera, they occur from Alaska to Tierra del Fuego, but most species are found in Cen ...
s of the Americas or a number of Australian passerines) during at least part of the winter, but this has not yet been proved.


References

{{Authority control Endemic birds of New Zealand Taxa named by Carl Jakob Sundevall