The yellowhead or mohua (''Mohoua ochrocephala'') is a small insectivorous
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 ...
bird
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 the
South Island
The South Island ( , 'the waters of Pounamu, Greenstone') is the largest of the three major islands of New Zealand by surface area, the others being the smaller but more populous North Island and Stewart Island. It is bordered to the north by ...
of
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 ...
. Once a common forest bird, its numbers declined drastically after the introduction of
rats
Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include ''Neotoma'' (pack rats), '' Bandicota'' (bandicoot ...
and
stoat
The stoat (''Mustela erminea''), also known as the Eurasian ermine or ermine, is a species of mustelid native to Eurasia and the northern regions of North America. Because of its wide circumpolar distribution, it is listed as Least Concern on th ...
s, and it is now near threatened.
Taxonomy
The yellowhead was
formally described in 1789 by the German naturalist
Johann Friedrich Gmelin
Johann Friedrich Gmelin (8 August 1748 – 1 November 1804) was a German natural history, naturalist, chemist, botanist, entomologist, herpetologist, and malacologist.
Education
Johann Friedrich Gmelin was born as the eldest son of Philipp F ...
in his revised and expanded edition of
Carl Linnaeus
Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...
's ''
Systema Naturae
' (originally in Latin written ' with the Orthographic ligature, ligature æ) is one of the major works of the Sweden, Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the syste ...
''. He placed it with the flycatchers in the
genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
''
Muscicapa'' and coined the
binomial name
In taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, altho ...
''Muscicapa ochrocephala''. The specific epithet is derived from the
Ancient Greek
Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
''ōkhros'' meaning "pale yellow" and ''-kephalos'' meaning "-headed". Gmelin based his account on the "yellow-headed fly-catcher" that had been described in 1783 by the English ornithologist
John Latham in his book ''A General Synopsis of Birds''. The naturalist
Joseph Banks
Sir Joseph Banks, 1st Baronet, (19 June 1820) was an English Natural history, naturalist, botanist, and patron of the natural sciences.
Banks made his name on the European and American voyages of scientific exploration, 1766 natural-history ...
had provided Latham with a watercolour painting of the bird by
Georg Forster
Johann George Adam Forster, also known as Georg Forster (; 27 November 1754 – 10 January 1794), was a German geography, geographer, natural history, naturalist, ethnology, ethnologist, travel literature, travel writer, journalist and revol ...
who had accompanied
James Cook
Captain (Royal Navy), Captain James Cook (7 November 1728 – 14 February 1779) was a British Royal Navy officer, explorer, and cartographer famous for his three voyages of exploration to the Pacific and Southern Oceans, conducted between 176 ...
on his
second voyage to the Pacific Ocean. The inscription on the painting includes the year 1774 and the location "Queen Charlotte's Sound".
Queen Charlotte Sound is on the north coast of the
South Island
The South Island ( , 'the waters of Pounamu, Greenstone') is the largest of the three major islands of New Zealand by surface area, the others being the smaller but more populous North Island and Stewart Island. It is bordered to the north by ...
of New Zealand. This picture is the
holotype
A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...
for the species and is in the collection of the
Natural History Museum
A natural history museum or museum of natural history is a scientific institution with natural history scientific collection, collections that include current and historical records of animals, plants, Fungus, fungi, ecosystems, geology, paleo ...
in London. The yellowhead is now one of three species placed in the genus ''
Mohoua'' that was introduced in 1837 by the French naturalist
René Lesson
René Primevère Lesson (20 March 1794 – 28 April 1849) was a French surgery, surgeon, natural history, naturalist, ornithologist, and herpetologist.
Biography
Lesson was born at Rochefort, Charente-Maritime, Rochefort, and entered the Naval ...
.
The species is
monotypic
In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...
: no
subspecies
In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...
are recognised.
[
The yellowhead was known in the 19th century as the "bush canary", after its trilling song.] It is also known as mohua from the Māori . Recent classification places this species and its close relative, the whitehead, in the family Mohouidae.
Distribution and habitat
The yellowhead and the whitehead have allopatric
Allopatric speciation () – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from ...
distributions as, conversely, the latter is found only in the North Island
The North Island ( , 'the fish of Māui', historically New Ulster) is one of the two main islands of New Zealand, islands of New Zealand, separated from the larger but less populous South Island by Cook Strait. With an area of , it is the List ...
and several small islands surrounding it. Although abundant in the 19th century, particularly in southern beech forests on the South Island
The South Island ( , 'the waters of Pounamu, Greenstone') is the largest of the three major islands of New Zealand by surface area, the others being the smaller but more populous North Island and Stewart Island. It is bordered to the north by ...
and Stewart Island / Rakiura
Stewart Island (, 'Aurora, glowing skies', officially Stewart Island / Rakiura, formerly New Leinster) is New Zealand's third-largest island, located south of the South Island, across Foveaux Strait.
It is a roughly triangular island wit ...
, mohua declined dramatically in the early 20th century due to the introduction of black rat
The black rat (''Rattus rattus''), also known as the roof rat, ship rat, or house rat, is a common long-tailed rodent of the stereotypical rat genus ''Rattus'', in the subfamily Murinae. It likely originated in the Indian subcontinent, but is n ...
s and mustelid
The Mustelidae (; from Latin , weasel) are a diverse family of carnivoran mammals, including weasels, badgers, otters, polecats, martens, grisons, and wolverines. Otherwise known as mustelids (), they form the largest family in the suborde ...
s; nesting in tree holes makes them more vulnerable to predators.
Today they have vanished from almost all of the South Island's forests and exist in less than 5% of their original range. On mainland South Island there is currently a small population of mohua in the Marlborough Sounds
The Marlborough Sounds (Māori language, te reo Māori: ''Te Tauihu-o-te-Waka'') are an extensive network of ria, sea-drowned valleys at the northern end of the South Island of New Zealand. The Marlborough Sounds were created by a combination ...
and around Arthur's Pass, but a quarter of the population lives in the beech forests of the Catlins
The Catlins (sometimes referred to as The Catlins Coast) comprise an area in the southeastern corner of the South Island of New Zealand. The area lies between Balclutha, New Zealand, Balclutha and Invercargill, straddling the boundary between ...
. The mohua number about 5000.
Behaviour and ecology
Foraging
Foraging is searching for wild food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce. Foraging theory is a branch of behavioral ecology that studies the foraging behavi ...
Mohua spends approximately three-quarters of their time foraging. The proportion of time used in foraging is highest during the premoult period and is lowest during the incubation period. In wild conditions, caterpillar
Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths).
As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder ...
s (Lepidoptera
Lepidoptera ( ) or lepidopterans is an order (biology), order of winged insects which includes butterflies and moths. About 180,000 species of the Lepidoptera have been described, representing 10% of the total described species of living organ ...
larvae) were the predominant food. In captivity, mohua were observed to prefer mealworms ('' Tenebrio molitor'' larvae) over other foods. However, due to mealworms' limited vitamin A and D content, a vitamin A deficiency in captive mohua was common. Although mohua are insectivore
file:Common brown robberfly with prey.jpg, A Asilidae, robber fly eating a hoverfly
An insectivore is a carnivore, carnivorous animal or plant which eats insects. An alternative term is entomophage, which can also refer to the Entomophagy ...
s, they have been observed to be opportunists who can eat various food items, including nuts and dried fruits. Foraging in captivity was mainly done between ground level and the shrub
A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...
layer. This differed from the foraging behaviour observed in wild conditions, where mohua spent over 99% of the time foraging exclusively in the shrub
A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...
and canopy layers of the forest, so they avoided feeding at ground level. Under both conditions, gleaning was the preferred foraging method despite foraging in different parts of the forest. Foraging behaviour differed in the podocarp forest on Ulva Island, and although gleaning was one of the main foraging methods, ripping was more common in the middle of spring (October). This correlated with greater foraging on the trunk and large branches of forest trees as opposed to the twigs, foliage and small branches during October. Twigs, foliage and small branches were generally preferred for foraging outside October. Rimu
''Dacrydium cupressinum'', commonly known as rimu, is a species of tree in the family Podocarpaceae. It is a dioecious evergreen conifer, reaching heights of up to , and can have a stout trunk (botany), trunk up to in diameter. It is endemis ...
and miro were the main foraging surfaces for mohua in the Ulva Island forest but were preferred at different rates depending on the time of year. Rimu
''Dacrydium cupressinum'', commonly known as rimu, is a species of tree in the family Podocarpaceae. It is a dioecious evergreen conifer, reaching heights of up to , and can have a stout trunk (botany), trunk up to in diameter. It is endemis ...
and Miro were equally preferred during the spring months of October and November, while Rimu was preferred over Miro during the summer months of December and January. However, during the November and December periods, mohua prefer a greater variety of species to forage from, including Rātā and Muttonbird Scrub. The foraging behaviour of mohua differs between podocarp and beech
Beech (genus ''Fagus'') is a genus of deciduous trees in the family Fagaceae, native to subtropical (accessory forest element) and temperate (as dominant element of Mesophyte, mesophytic forests) Eurasia and North America. There are 14 accepted ...
forests, as there is a greater dependence on foliage for scanning and foraging in both red and mountain
A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher t ...
beech forests. In both red and mountain beech forests, the trucks in the upper shrub layer were foraged from equally to the foliage, but in the upper canopy, the foliage was almost used exclusively, and the truck was not foraged from at all. red and mountain beech differ in foraging use in the lower canopy because, in red beech forests, the foliage and other surfaces such as the trunk, small branches, large branches and dead wood are all readily foraged from by mohua, while in mountain beech forests, the main surface used was the foliage. However, other surfaces were also foraged from. Like the podocarp forests of Ulva Island, ripping in beech forests was a common foraging method mainly due to mohua foraging on standing dead beech tree trunks.
Reproduction
Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. There are two forms of reproduction: Asexual reproduction, asexual and Sexual ...
and Incubation
Mohua are cooperative breeders
Cooperative breeding is a social system characterized by alloparental care: offspring receive care not only from their parents, but also from additional group members, often called helpers. Cooperative breeding encompasses a wide variety of group s ...
, which is not currently beneficial for their population growth as there are fewer breeding pairs than there could be, resulting in fewer offspring
In biology, offspring are the young creation of living organisms, produced either by sexual reproduction, sexual or asexual reproduction. Collective offspring may be known as a brood or progeny. This can refer to a set of simultaneous offspring ...
overall. However, this behaviour is an evolutionary adaptation to the lack of resources, which is beneficial if there is an abundance of mohua. Mohua cooperate by having a primary pair that breeds and is assisted by subordinate
A hierarchy (from Greek: , from , 'president of sacred rites') is an arrangement of items (objects, names, values, categories, etc.) that are represented as being "above", "below", or "at the same level as" one another. Hierarchy is an importan ...
mohua called secondaries. Not all mohua pairs have secondaries. Secondaries can form their own pairs and some breed, although they are generally less successful in producing fledglings than the primary pair. The secondary pairs were in the territory
A territory is an area of land, sea, or space, belonging or connected to a particular country, person, or animal.
In international politics, a territory is usually a geographic area which has not been granted the powers of self-government, ...
of the primary pair, so they provided assistance when mobbing
Mobbing, as a sociological term, refers either to bullying in any context, or specifically to that within the workplace, especially when perpetrated by a group rather than an individual.
Psychological and health effects
Victims of workplace mo ...
intruders, foraged together with the primary pair and assisted with territorial singing, while secondary helpers were actively feeding the nestlings, assisting with incubation and exhibiting territorial behaviour. The male secondary helpers mainly assisted with territorial singing, while the female secondary helpers could not sing but could assist with incubation. The secondary helpers did not necessarily have to be related to the primary pair. However, these were generally males who became the primary male in the territory if the previous primary male had disappeared before the next breeding season. Only male mohua sang and defended their territory against males from neighbouring territories with singing duels. The primary males also chased other mohua who were intruders or secondaries. The female mohua were exclusively responsible for the building of nests and the incubation of the eggs. However, the male guarded the female during this period and fed her while she was incubating. Mohua are hole-nesting birds, meaning they build their nests within tree cavities. Like other birds, mohua weave cup-shaped nests using soft materials such as moss
Mosses are small, non-vascular plant, non-vascular flowerless plants in the taxonomic phylum, division Bryophyta (, ) ''sensu stricto''. Bryophyta (''sensu lato'', Wilhelm Philippe Schimper, Schimp. 1879) may also refer to the parent group bryo ...
, grass
Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family (biology), family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and spe ...
, filmy ferns and lichen
A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...
s. Mohua nesting holes are always found on large, old trees and anywhere from 1.7 m to over 31 m in the tree's cavities. The tree cavities used were mainly on the trunk, but dead branches with rotten wood were also utilised. Knot holes on tree trunks were the preferred place for mohua to build their nests. Mohua produces clutches of 1 to 5 eggs and can produce a second clutch if the female has enough food. If the female mohua does not get enough food, the breeding season will be short and late. When the primary female laid a second clutch, the chicks were fed by the primary male and the secondaries, while the female dedicated her time to incubating the new clutch. This is beneficial for the fledglings' survival as they could have more food and, therefore, energy to survive and grow. Mohua breeding differs, causing incubation times to range from October to December.
Movement
Flocks of up to 25 mohua can occur from January as this is outside their incubation times, so they are not territorial during these times. These flocks can sometimes consist of many mohua families, which causes the flocks to be louder overall. The movement of these flocks attract other bird species to follow mohua as they forage in similar areas for similar foods. The other bird species that flock and forage with mohua are the yellow
Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In t ...
and red-crowned parakeets, orange-fronted parakeets, fantail, tomtits, brown creepers, grey warblers, silvereyes and bellbirds. All of these species have similarities to the mohua in various ways, such as the parakeets, which are also hole-nesting birds; the brown creepers are in the same genus as the mohua and have certain sympatric
In biology, two closely related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter each other. An initially interbreeding population that splits into two or more distinct spe ...
distributions spanning the South Island
The South Island ( , 'the waters of Pounamu, Greenstone') is the largest of the three major islands of New Zealand by surface area, the others being the smaller but more populous North Island and Stewart Island. It is bordered to the north by ...
; and the rest of the birds are all New Zealand native passerine forest birds that are small to medium-sized which makes sense as to why these birds have similar foraging habits. This multi-species flocking technique will likely help with more effective foraging as more individual birds can spot abundant prey. Mohua leads these flocks past bodies of water and through valleys to forage, allowing for distances of over 100 ha to be foraged from, which is much greater than during territorial times where the distances range up to 7 ha.
Conservation
In New Zealand, mohua have the status of a ''protected threatened endemic'' species. Conservation efforts are being made to ensure its survival and mohua populations have been established on several predator-free offshore islands, such as Breaksea Island in Fiordland
Fiordland (, "The Pit of Tattooing", and also translated as "the Shadowlands"), is a non-administrative geographical region of New Zealand in the south-western corner of the South Island, comprising the western third of Southland. Most of F ...
and Ulva Island. Birds have been captive-bred at Orana Park in Christchurch
Christchurch (; ) is the largest city in the South Island and the List of cities in New Zealand, second-largest city by urban area population in New Zealand. Christchurch has an urban population of , and a metropolitan population of over hal ...
.
The behaviour of mohua can, in some cases, assist with the species' success or cause its demise, depending on the species it interacts with. Long-tailed cuckoos parasitise mohua nests by laying their eggs within mohua inhabited tree hole nests. After hatching, the young cuckoos will attempt to push the mohua chicks out of the nest but have a lower chance of success in these tree hole nests as compared to typical nests as the sides of the nests are generally supported by the edges of the tree hole causing the mohua chicks to survive. Another way tree hole nests benefit mohua is that the openings to these knot tree holes which mohua chooses to nest in are usually too small for the adult long-tailed cuckoo to enter. Adult long-tailed cuckoos also remove the eggs and nestlings from mohua nests if they cannot fit in the tree hole and lay their eggs. This tree hole nesting strategy prevents the predation of mohua by long-tailed cuckoos and other carnivorous birds such as the falcons and morepork. Although cuckoos affect mohua success in producing offspring
In biology, offspring are the young creation of living organisms, produced either by sexual reproduction, sexual or asexual reproduction. Collective offspring may be known as a brood or progeny. This can refer to a set of simultaneous offspring ...
, they are generally less effective against mohua than other parasitised bird species. The conservation problem with mohua behaviour arises when speaking about invasive mammal
A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
ian predators, which the mohua are not adapted to compared to non-native bird species. Mohua are susceptible to predation
Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...
by stoat
The stoat (''Mustela erminea''), also known as the Eurasian ermine or ermine, is a species of mustelid native to Eurasia and the northern regions of North America. Because of its wide circumpolar distribution, it is listed as Least Concern on th ...
s and ship rats
The black rat (''Rattus rattus''), also known as the roof rat, ship rat, or house rat, is a common long-tailed rodent of the stereotypical rat genus '' Rattus'', in the subfamily Murinae. It likely originated in the Indian subcontinent, but is ...
because mohua nest in tree holes, which does not allow for a quick escape if a predator were to enter the tree hole. The effects of predation on mohua by these mammals generally depend on the forest condition. This is because when it is a mast year in a beech tree forest, the mast causes mice
A mouse (: mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...
populations to grow, which means more food for stoat
The stoat (''Mustela erminea''), also known as the Eurasian ermine or ermine, is a species of mustelid native to Eurasia and the northern regions of North America. Because of its wide circumpolar distribution, it is listed as Least Concern on th ...
s, causing an increase in stoat population. This increase in stoat population is dangerous for all possible prey species in that forest because after preying on the mice, the stoats are still in high quantities and can easily shift their predation efforts onto native forest birds that live in these beech forests, such as mohua. Since female mohua must remain on the eggs for most of the incubation period and are the only ones that do incubate, this leaves them as the primary target for predation
Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...
as it has little chance of survival after the stoat has entered the tree hole. With the lack of female mohua and nestlings, which are also preyed upon, the following breeding season will have reduced breeding pairs, so this singular predation event will make it difficult for the mohua population to recover. These behaviours that mohua exhibit effectively avoid predation by avian predators but make them susceptible to mammalian predators that they had not evolved
Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...
around.
In 2003, 39 mohua were translocated from Breaksea Island to predator-free Codfish Island / Whenua Hou, and more were introduced to Whenua Hōu from the Catlins in 2018, increasing the island's population to about 1000. More releases are planned to islands in Fiordland.
Pest control efforts by the Department of Conservation have managed to stabilise some mainland mohua populations. For example, where biodegradable 1080 poison was used to control rats in the Dart valley, there was a more than 80% survival rate, compared with just 10% in untreated areas. The population of mohua in the Landsborough valley has increased four-fold since 1998, thanks to an intensive programme of pest control, including aerial 1080. The population is now strong enough for birds to be transferred out to establish a new population on Resolution Island. Similar aerial 1080 operations in the Catlins and the Hurunui, Hawdon and Eglinton valleys have had equally encouraging results. DOC and TBfree New Zealand noted in March 2014 that there was a significant repopulation in the Catlins of other avian species, including bellbird and tomtit due to the reduction of predators.
Popular culture
Since the redesign of New Zealand's currency in 1991 a yellowhead has appeared on the reverse side of the New Zealand $100 note.
References
Literature
*
External links
Mōhua Charitable Trust
*
{{Taxonbar, from=Q1066503
Mohoua
Birds of the South Island
Birds described in 1789
Taxa named by Johann Friedrich Gmelin
Endemic birds of New Zealand