New Zealand wren
Encyclopedia
The New Zealand wrens, Acanthisittidae, are a family
of tiny passerine
s endemic
to New Zealand
. They were represented by six known species
in four or five genera
, although only two species survive in two genera 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 recentstudies suggest that they form a third, most ancient, suborder Acanthisitti and have no living close relatives at all. They are called "wrens" due to similarities in appearance and behaviour to the true wren
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 Rock Wren
being restricted to alpine areas. Both the remaining species are poor fliers and four of the five extinct species are known to or are suspected of having been flightless (based on observations of living birds and the size of their sternum
); along with the Long-legged Bunting
from the Canary Islands
they are the only passerines known to have lost the ability to fly. Of the species for which the plumage
is known 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 passerines for the most part sedentary.
New Zealand wrens, like many New Zealand birds, suffered several extinctions after the arrival of humans in New Zealand. Two species went extinct after the arrival of the Māori and the Polynesian Rat
, and are known today only from fossil
remains; a third, the Stephen's Island Wren went extinct on the main islands, surviving only as a relict
population on Stephens Island
in the Cook Strait. Two species, the Stephens Island Wren
and the Bush Wren
, became extinct after the arrival of Europeans, with the Bush Wren surviving until 1972. Of the two remaining species the Rifleman
is still common on both North and South Island, while the South Island Wren is restricted to the alpine areas of South Island and is considered vulnerable.
assigned the New Zealand wrens to the subocines related to the cotinga
s and pitta
s (and gave the family the name Xenicidae). Later they were thought to be closer to the ovenbird
s and antbird
s. Sibley’s 1970 study comparing egg-white protein
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 subocines 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
82-85 mya (million years ago), though a pre-Paleogene
origin of passerines is highly disputed and tends to be rejected in more recent studies.
It must be remarked that Ericson et al.'s study used an entirely unreliable molecular clock
. The Cretaceous
date it suggested it generally not taken seriously by the majority of researchers today.
As there is no reason to believe that passerines were flightless when they arrived on New Zealand (that apomorphy is extremely rare and unevenly distributed in Passeriformes), they are not required by present theories to have been distinct in the Mesozoic
. As unequivocal Passeriformes are known from Australia
some 55 mya, it is likely that the acanthisittids' ancestors arrived in the Late Paleocene from Australia or the then-temperate
Antarctic
coasts. Plate tectonics
indicates that the shortest distance between New Zealand and those two continents was roughly 1,500 km (not quite 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 c.2,500 km (1,550 miles) from Antactica.
The extant species are closely related and thought to be descendents of birds that survived a genetic bottleneck caused by the marine transgression during the Oligocene
when most of New Zealand was underwater.
The relationships between the genera and species are poorly understood. The extant genus Acanthisitta has one species, the Rifleman
, and the other surviving genus, Xenicus includes the Rock Wren and the recently extinct Bush Wren
. Some authorities have retained the Stephens Island Wren
in Xenicus as well, but it is often afforded its own monotpic 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.
and restricted to the main islands of New Zealand and their offshore islands; they have not been found on any of the outer islands of New Zealand (such as the Chathams
or the Kermadec Islands
). Prior to the arrival of humans in New Zealand they had a widespread distribution across North, South and Stewart Island/Rakiura
. The range of the Rifleman and Bush Wren included southern beech
forest and podocarp-broadleaf forest, with the range of the Bush Wren also including coastal forest and scrub, particularly the Stewart Island subspecies. The New Zealand Rockwren is specialised for the alpine
environment, in areas of low scrub and scree from 900 m up to 2,400 m. Contrary to its other common name (the South Island Wren) fossil
evidence shows it was more widespread in the past and lived on North Island. The Stephens Island Wren
was once thought to have been restricted to the tiny Stephens Island
in the Cook Strait
, but fossil evidence has shown the species was once widespread on both North and South Island. The Stout-legged Wren was similarly found on both islands, but fossils of the Long-billed Wren have only been found on 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 Rockwren is now restricted to 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
s of introduced exotic pine
s, principally the Monterey Pine
. 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 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, however they are also absent from their normal territories. It is suspected that they may enter a state of torpor
(like the hummingbird
s of the Americas or a number of Australian passerines) during at least part of the winter but this has not yet been proved.
. The South Island Wren (and probably the Bush Wren) weighs between 14-22g, and the extinct Long-billed Wren around 30g.
The plumage
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 the Stephens Island Wren
have a prominent supercilium above the eye. The plumages of males and females were alike in the Stephens Island Wren and the Bush Wren; the Rock Wren shows slight sexual dimorphism
in its plumage and differences between the plumage of Riflemen
are prononced, with the male having bright green upperparts and the female being duller and browner.
Both the Rock Wren and the Rifleman also show sexual dimorphism in size, unusually for passerine
s it is the female that 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
.
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 the Stephens Island Wren. The skeleton
s of these species have massively reduced keels in the sternum
, and the flight feather
s of the Stephens Island Wren also indicate flightlessness. Contemporary accounts of the Stephens Island Wrens describe the species as scurrying on the ground rather than flying.
Genus Xenicus
Genus Pachyplichas
†Pachyplichas jagmi
Genus Dendroscansor
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of tiny passerine
Passerine
A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...
s endemic
Endemic (ecology)
Endemism is the ecological state of being unique to a defined geographic location, such as an island, nation or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. For example, all species of lemur are endemic to the...
to New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. They were represented by six known species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in four or five genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
, although only two species survive in two genera 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 recentstudies suggest that they form a third, most ancient, suborder Acanthisitti and have no living close relatives at all. They are called "wrens" due to similarities in appearance and behaviour to the true wren
Wren
The wrens are passerine birds in the mainly New World family Troglodytidae. There are approximately 80 species of true wrens in approximately 20 genera....
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 Rock Wren
Rock Wren (New Zealand)
The New Zealand Rockwren , or Rock Wren, is a small New Zealand wren endemic to the South Island of New Zealand. It is sometimes known as the South Island Wren, a name used to separate it from the unrelated Rock Wren of North America...
being restricted to alpine areas. Both the remaining species are poor fliers and four of the five extinct species are known to or are suspected of having been flightless (based on observations of living birds and the size of their sternum
Sternum
The sternum or breastbone is a long flat bony plate shaped like a capital "T" located anteriorly to the heart in the center of the thorax...
); along with the Long-legged Bunting
Long-legged Bunting
The Long-legged Bunting is an extinct flightless species of bunting. It was distinguishable by its long legs and short wings, and it inhabited the Canary Islands...
from the Canary Islands
Canary Islands
The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...
they are the only passerines known to have lost the ability to fly. Of the species for which the plumage
Plumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
is known they are drab coloured birds with brown-green plumage. They form monogamous
Monogamy
Monogamy /Gr. μονός+γάμος - one+marriage/ a form of marriage in which an individual has only one spouse at any one time. In current usage monogamy often refers to having one sexual partner irrespective of marriage or reproduction...
pair bonds to raise their young laying their eggs in small nests in trees or amongst rocks. They are diurnal
Diurnal animal
Diurnality is a plant or animal behavior characterized by activity during the day and sleeping at night.-In animals:Animals that are not diurnal might be nocturnal or crepuscular . Many animal species are diurnal, including many mammals, insects, reptiles and birds...
and like all New Zealand passerines for the most part sedentary.
New Zealand wrens, like many New Zealand birds, suffered several extinctions after the arrival of humans in New Zealand. Two species went extinct after the arrival of the Māori and the Polynesian Rat
Polynesian Rat
The Polynesian Rat, or Pacific Rat , known to the Māori as kiore, is the third most widespread species of rat in the world behind the Brown Rat and Black Rat. The Polynesian Rat originates in Southeast Asia but, like its cousins, has become well travelled – infiltrating Fiji and most Polynesian...
, and are known today only from fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
remains; a third, the Stephen's Island Wren went extinct on the main islands, surviving only as a relict
Relict
A relict is a surviving remnant of a natural phenomenon.* In biology a relict is an organism that at an earlier time was abundant in a large area but now occurs at only one or a few small areas....
population on Stephens Island
Stephens Island, New Zealand
Stephens Island is at the northern most tip of the Marlborough Sounds in the South Island of New Zealand. It lies two kilometres to the northeast of Cape Stephens, the northernmost point of D'Urville Island. The Māori call the island Takapourewa but Stephens Island is the commonly used name...
in the Cook Strait. Two species, the Stephens Island Wren
Stephens Island Wren
The Stephens Island Wren or Lyall's Wren was a nocturnal, flightless, insectivorous passerine.-Habitat:...
and the Bush Wren
Bush Wren
The Bushwren , Bush Wren, or Mātuhituhi in Maori, was a very small and almost flightless bird endemic to New Zealand. It grew to about 9 cm long and 16 g in weight. It fed mostly on invertebrates which it captured by running along the branches of trees...
, became extinct after the arrival of Europeans, with the Bush Wren surviving until 1972. Of the two remaining species the Rifleman
Rifleman (bird)
The Rifleman is a small insectivorous passerine bird that is endemic to New Zealand. It belongs to the Acanthisittidae family, also known as the New Zealand wrens, of which it is one of only two surviving species...
is still common on both North and South Island, while the South Island Wren is restricted to the alpine areas of South Island and is considered vulnerable.
Taxonomy and evolution
The taxonomy of the New Zealand wrens has been a subject of considerable debate since their discovery, although it has long been known that they are an unusual family. In the 1880s ForbesHenry Ogg Forbes
Henry Ogg Forbes was a Scottish explorer, ornithologist, and botanist. Educated at Aberdeen Grammar School, the University of Aberdeen and the University of Edinburgh, he was primarily active in the Moluccas and New Guinea, he served as director of the Canterbury Museum in New Zealand between...
assigned the New Zealand wrens to the subocines related to the cotinga
Cotinga
The cotingas are a large family of passerine bird species found in Central America and tropical South America. Cotingas are birds of forests or forest edges, which mostly eat fruit or insects and fruit. Comparatively little is known about this diverse group, although all have broad bills with...
s and pitta
Pitta
Pitta may stand for:*Pittas, a family of tropical birds*Pitta bread *Pitta , an island in the Dodecanese archipelago, in the Aegean Sea...
s (and gave the family the name Xenicidae). Later they were thought to be closer to the ovenbird
Ovenbird
The Ovenbird is a small songbird of the New World warbler family . This migratory bird breeds in eastern North America and moves south in winter.-Taxonomy:...
s and antbird
Antbird
The antbirds are a large family, Thamnophilidae, of passerine birds found across subtropical and tropical Central and South America, from Mexico to Argentina. There are more than 200 species, known variously as antshrikes, antwrens, antvireos, fire-eyes, bare-eyes and bushbirds...
s. Sibley’s 1970 study comparing egg-white protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
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 subocines 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
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
82-85 mya (million years ago), though a pre-Paleogene
Paleogene
The Paleogene is a geologic period and system that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic Era...
origin of passerines is highly disputed and tends to be rejected in more recent studies.
It must be remarked that Ericson et al.'s study used an entirely unreliable molecular clock
Molecular clock
The molecular clock is a technique in molecular evolution that uses fossil constraints and rates of molecular change to deduce the time in geologic history when two species or other taxa diverged. It is used to estimate the time of occurrence of events called speciation or radiation...
. The Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
date it suggested it generally not taken seriously by the majority of researchers today.
As there is no reason to believe that passerines were flightless when they arrived on New Zealand (that apomorphy is extremely rare and unevenly distributed in Passeriformes), they are not required by present theories to have been distinct in the Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
. As unequivocal Passeriformes are known from Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
some 55 mya, it is likely that the acanthisittids' ancestors arrived in the Late Paleocene from Australia or the then-temperate
Temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...
Antarctic
Antarctic
The Antarctic is the region around the Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica and the ice shelves, waters and island territories in the Southern Ocean situated south of the Antarctic Convergence...
coasts. Plate tectonics
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...
indicates that the shortest distance between New Zealand and those two continents was roughly 1,500 km (not quite 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 c.2,500 km (1,550 miles) from Antactica.
The extant species are closely related and thought to be descendents of birds that survived a genetic bottleneck caused by the marine transgression during the Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
when most of New Zealand was underwater.
The relationships between the genera and species are poorly understood. The extant genus Acanthisitta has one species, the Rifleman
Rifleman (bird)
The Rifleman is a small insectivorous passerine bird that is endemic to New Zealand. It belongs to the Acanthisittidae family, also known as the New Zealand wrens, of which it is one of only two surviving species...
, and the other surviving genus, Xenicus includes the Rock Wren and the recently extinct Bush Wren
Bush Wren
The Bushwren , Bush Wren, or Mātuhituhi in Maori, was a very small and almost flightless bird endemic to New Zealand. It grew to about 9 cm long and 16 g in weight. It fed mostly on invertebrates which it captured by running along the branches of trees...
. Some authorities have retained the Stephens Island Wren
Stephens Island Wren
The Stephens Island Wren or Lyall's Wren was a nocturnal, flightless, insectivorous passerine.-Habitat:...
in Xenicus as well, but it is often afforded its own monotpic 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.
Distribution, habitat and movements
The New Zealand wrens are endemicEndemic (ecology)
Endemism is the ecological state of being unique to a defined geographic location, such as an island, nation or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. For example, all species of lemur are endemic to the...
and restricted to the main islands of New Zealand and their offshore islands; they have not been found on any of the outer islands of New Zealand (such as the Chathams
Chatham Islands
The Chatham Islands are an archipelago and New Zealand territory in the Pacific Ocean consisting of about ten islands within a radius, the largest of which are Chatham Island and Pitt Island. Their name in the indigenous language, Moriori, means Misty Sun...
or the Kermadec Islands
Kermadec Islands
The Kermadec Islands are a subtropical island arc in the South Pacific Ocean northeast of New Zealand's North Island, and a similar distance southwest of Tonga...
). Prior to the arrival of humans in New Zealand they had a widespread distribution across North, South and Stewart Island/Rakiura
Stewart Island/Rakiura
Stewart Island/Rakiura is the third-largest island of New Zealand. It lies south of the South Island, across Foveaux Strait. Its permanent population is slightly over 400 people, most of whom live in the settlement of Oban.- History and naming :...
. The range of the Rifleman and Bush Wren included southern beech
Nothofagus
Nothofagus, also known as the southern beeches, is a genus of 35 species of trees and shrubs native to the temperate oceanic to tropical Southern Hemisphere in southern South America and Australasia...
forest and podocarp-broadleaf forest, with the range of the Bush Wren also including coastal forest and scrub, particularly the Stewart Island subspecies. The New Zealand Rockwren is specialised for the alpine
Alpine climate
Alpine climate is the average weather for a region above the tree line. This climate is also referred to as mountain climate or highland climate....
environment, in areas of low scrub and scree from 900 m up to 2,400 m. Contrary to its other common name (the South Island Wren) fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
evidence shows it was more widespread in the past and lived on North Island. The Stephens Island Wren
Stephens Island Wren
The Stephens Island Wren or Lyall's Wren was a nocturnal, flightless, insectivorous passerine.-Habitat:...
was once thought to have been restricted to the tiny Stephens Island
Stephens Island
Stephens Island may refer to:* Stephens Island , Queensland, Australia* Stephens Island , Queensland, Australia* Stephens Island , Canada* Stephens Island , Canada* Stephens Island, New Zealand...
in the Cook Strait
Cook Strait
Cook Strait is the strait between the North and South Islands of New Zealand. It connects the Tasman Sea on the west with the South Pacific Ocean on the east....
, but fossil evidence has shown the species was once widespread on both North and South Island. The Stout-legged Wren was similarly found on both islands, but fossils of the Long-billed Wren have only been found on 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.
Plantation
A plantation is a long artificially established forest, farm or estate, where crops are grown for sale, often in distant markets rather than for local on-site consumption...
s of introduced exotic pine
Pine
Pines are trees in the genus Pinus ,in the family Pinaceae. They make up the monotypic subfamily Pinoideae. There are about 115 species of pine, although different authorities accept between 105 and 125 species.-Etymology:...
s, principally the Monterey Pine
Monterey Pine
The Monterey Pine, Pinus radiata, family Pinaceae, also known as the Insignis Pine or Radiata Pine is a species of pine native to the Central Coast of California....
. 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
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
. 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 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, however they are also absent from their normal territories. It is suspected that they may enter a state of torpor
Torpor
Torpor, sometimes called temporary hibernation is a state of decreased physiological activity in an animal, usually characterized by a reduced body temperature and rate of metabolism. Animals that go through torpor include birds and some mammals such as mice and bats...
(like the hummingbird
Hummingbird
Hummingbirds are birds that comprise the family Trochilidae. They are among the smallest of birds, most species measuring in the 7.5–13 cm range. Indeed, the smallest extant bird species is a hummingbird, the 5-cm Bee Hummingbird. They can hover in mid-air by rapidly flapping their wings...
s of the Americas or a number of Australian passerines) during at least part of the winter but this has not yet been proved.
Morphology
New Zealand wrens are tiny birds; the Rifleman being the smallest of New Zealand's birds. Their length ranges from 7 cm to 10 cm, and their weight from as little as 5-7g for the Rifleman to an estimated 50g for the extinct Stout-legged WrenStout-legged Wren
The Stout-legged Wren or Yaldwin's Wren is an extinct species of New Zealand wren, a family of small birds endemic to New Zealand.-History and etymology:...
. The South Island Wren (and probably the Bush Wren) weighs between 14-22g, and the extinct Long-billed Wren around 30g.
The plumage
Plumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
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 the Stephens Island Wren
Stephens Island Wren
The Stephens Island Wren or Lyall's Wren was a nocturnal, flightless, insectivorous passerine.-Habitat:...
have a prominent supercilium above the eye. The plumages of males and females were alike in the Stephens Island Wren and the Bush Wren; the Rock Wren shows slight sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in its plumage and differences between the plumage of Riflemen
Rifleman (bird)
The Rifleman is a small insectivorous passerine bird that is endemic to New Zealand. It belongs to the Acanthisittidae family, also known as the New Zealand wrens, of which it is one of only two surviving species...
are prononced, with the male having bright green upperparts and the female being duller and browner.
Both the Rock Wren and the Rifleman also show sexual dimorphism in size, unusually for passerine
Passerine
A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...
s it is the female that 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
Claw
A claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. However, the word "claw" is also often used in reference to an invertebrate. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end...
.
The New Zealand wrens evolved in the absence of mammals for many millions of years, and the family was losing
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
the ability to fly
Bird flight
Flight is the main mode of locomotion used by most of the world's bird species. Flight assists birds while feeding, breeding and avoiding predators....
. Three species are thought to have lost the power of flight, the Stout-legged Wren, the Long-billed Wren and the Stephens Island Wren. The skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
s of these species have massively reduced keels in the sternum
Sternum
The sternum or breastbone is a long flat bony plate shaped like a capital "T" located anteriorly to the heart in the center of the thorax...
, and the flight feather
Feather
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...
s of the Stephens Island Wren also indicate flightlessness. Contemporary accounts of the Stephens Island Wrens describe the species as scurrying on the ground rather than flying.
Species
- Genus Acanthisitta
- RiflemanRifleman (bird)The Rifleman is a small insectivorous passerine bird that is endemic to New Zealand. It belongs to the Acanthisittidae family, also known as the New Zealand wrens, of which it is one of only two surviving species...
(Titipounamu):
- Rifleman
Xenicus
Xenicus is a genus of birds in the family Acanthisittidae. It contains New Zealand wrens.-Species:*New Zealand Rockwren, Xenicus gilviventris*Bushwren, †Xenicus longipes *Stephens Island Wren, †Xenicus lyalli...
- †Bush WrenBush WrenThe Bushwren , Bush Wren, or Mātuhituhi in Maori, was a very small and almost flightless bird endemic to New Zealand. It grew to about 9 cm long and 16 g in weight. It fed mostly on invertebrates which it captured by running along the branches of trees...
, Xenicus longipes - New Zealand Rockwren or South Island Wren, Xenicus gilviventris
- †Stephens Island WrenStephens Island WrenThe Stephens Island Wren or Lyall's Wren was a nocturnal, flightless, insectivorous passerine.-Habitat:...
, Xenicus lyalli
Pachyplichas
Pachyplichas is a genus containing two extinct species of New Zealand wren, a family of small birds endemic to New Zealand.-Species:* P. yaldwyni – South Island, New Zealand* P. jagmi – North Island, New Zealand...
- †Stout-legged WrenStout-legged WrenThe Stout-legged Wren or Yaldwin's Wren is an extinct species of New Zealand wren, a family of small birds endemic to New Zealand.-History and etymology:...
,
Pachyplichas jagmi
Pachyplichas jagmi is an extinct species of New Zealand wren, a family of small birds endemic to New Zealand.-History and etymology:The holotype is a right tarsometatarsus collected on 25 August 1978 from the Ruakuri Cave in the Waitomo District of the North Island of New Zealand...
- †Long-billed WrenLong-billed Wren (New Zealand)The Long-billed Wren was a species of New Zealand wren endemic to the South Island of New Zealand. It was the only species in the genus Dendroscansor...
, Dendroscansor decurvirostris