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  • KIWI (BIRD)

    Kiwi (/ˈkiːwiː/ KEE-wee)[4] are flightless birds endemic to New Zealand of the order Apterygiformes. The five extant species fall into the family Apterygidae (/ˌæptəˈrɪdʒədiː/) and genus Apteryx (/ˈæptərɪks/).[5] Approximately the size of a domestic chicken, kiwi are the smallest ratites (which also include ostriches, emus, rheas, cassowaries and the extinct elephant birds and moa).

    DNA sequence comparisons have yielded the conclusion that kiwi are much more closely related to the extinct Malagasy elephant birds than to the moa with which they shared New Zealand.[6] There are five recognised species, four of which are currently listed as vulnerable, and one of which is near threatened. All species have been negatively affected by historic deforestation, but their remaining habitat is well protected in large forest reserves and national parks. At present, the greatest threat to their survival is predation by invasive mammalian predators.

    The vestigial wings are so small as to be invisible under their bristly, hair-like, two-branched feathers. Kiwi eggs are one of the largest in proportion to body size (up to 20% of the female’s weight) of any order of bird in the world.[7] Other unique adaptations of kiwi, such as short and stout legs and using their nostrils at the end of their long beak to detect prey before they see it, have helped the bird to become internationally well known.

    The kiwi is recognised as an icon of New Zealand, and the association is so strong that the term Kiwi is used internationally as the colloquial demonym for New Zealanders.[8]

    Etymology

    The Māori language word kiwi is generally accepted to be “of imitative origin” from the call.[9] However, some linguists derive the word from Proto-Nuclear Polynesian *kiwi, which refers to Numenius tahitiensis, the bristle-thighed curlew, a migratory bird that winters in the tropical Pacific islands.[10] With its long decurved bill and brown body, the curlew resembles the kiwi. So when the first Polynesian settlers arrived, they may have applied the word kiwi to the newfound bird.[11] The bird’s name is spelled with a lower-case k and, being a word of Māori origin, normally stays as kiwi when pluralised.[12][failed verification]

    The genus name Apteryx is derived from Ancient Greek ‘without wing’: a- (ἀ-), ‘without’ or ‘not’; ptéryx (πτέρυξ), ‘wing’.[13]

    Taxonomy and systematics

    Although it was long presumed that the kiwi was closely related to the other New Zealand ratites, the moa, recent DNA studies have identified its closest relative as the extinct elephant bird of Madagascar,[6][14] and among extant ratites, the kiwi is more closely related to the emu and the cassowaries than to the moa.[6][15]

    Research published in 2013 on an extinct genus, Proapteryx, known from the Miocene deposits of the Saint Bathans Fauna, found that it was smaller and probably capable of flight, supporting the hypothesis that the ancestor of the kiwi reached New Zealand independently from moas, which were already large and flightless by the time kiwi appeared.[16]

    Species

    There are five known species of kiwi, with a number of subspecies.

    A. haastiiA. owenii
    A. australisA. rowiA. mantelli

    Relationships in the genus Apteryx[17]

    ImageScientific nameCommon nameDistributionDescription
    Apteryx haastiiGreat spotted kiwi or roroaNew ZealandThe largest species, standing about 45 cm (18 in) tall, with females weighing about 3.3 kg (7.3 lb) and males about 2.4 kg (5.3 lb). It has grey-brown plumage with lighter bands. The female lays one egg a year, which both parents incubate. The population is estimated at over 20,000, distributed through the more mountainous parts of northwest Nelson, the northern West Coast, and the Southern Alps of the South Island.[18]
    Apteryx oweniiLittle spotted kiwiKapiti IslandA small kiwi the size of a bantam, standing 25 cm (9.8 in) tall, with the female weighing 1.3 kg (2.9 lb). She lays one egg, which is incubated by the male. This small, docile kiwi is unable to withstand predation by introduced pigs, stoats and cats, leading to its extinction on the mainland. There are about 1350 on Kapiti Island and it has been introduced to other predator-free islands, where it appears to be getting established with about 50 on each island.[19]
    Apteryx rowiOkarito kiwi, rowi or Okarito brown kiwiSouth IslandThe Okarito kiwi, first identified as a new species in 1994,[20] is slightly smaller than the North Island brown kiwi, with a greyish tinge to the plumage and sometimes white facial feathers. Females lay up to three eggs in a season, each one in a different nest. Male and female both incubate. Distribution is now limited to a small area on the West Coast, but studies of ancient DNA have shown that, in prehuman times, it was far more widespread on the western side of the South Island and lived in the lower half of the North Island, where it was the only kiwi species detected.[21]
    Apteryx australisSouthern brown kiwi, tokoeka or common kiwiSouth IslandAlmost as big as the great spotted kiwi and similar in appearance to the brown kiwi, though its plumage is lighter in colour. It is relatively numerous. Ancient DNA studies have shown that, in prehuman times, the distribution of this species included the east coast of the South Island.[21] Several subspecies are recognised:The Stewart Island southern brown kiwi, Apteryx australis lawryi, is from Stewart Island/Rakiura.[22]The northern Fiordland tokoeka (Apteryx australis ?) and southern Fiordland tokoeka (Apteryx australis ?) live in Fiordland, the remote southwest part of the South Island. These subspecies of tokoeka are relatively common and are nearly 40 cm (16 in) tall.[citation needed]The Haast southern brown kiwi or Haast tokoeka, Apteryx australis ‘Haast’, is the rarest taxon of kiwi with only about 300 individuals. It was identified as a distinct form in 1993. It occurs only in a restricted area in the Haast Range of the Southern Alps at an altitude of 1,500 m (4,900 ft). This form is distinguished by a more strongly downcurved bill and more rufous plumage.[22]
    Apteryx mantelli or Apteryx australisNorth Island brown kiwiNorth IslandA. mantelli (or A. australis before 2000 and still in some sources) females stand about 40 cm (16 in) tall and weigh about 2.8 kg (6.2 lb), while the males weigh about 2.2 kg (4.9 lb). The plumage is streaky red-brown and spiky. The female usually lays two eggs, which are incubated by the male.[23] The North Island brown has demonstrated a remarkable resilience: it adapts to a wide range of habitats, including non-native forests and some farmland. It is widespread in the northern two-thirds of the North Island and is the most common kiwi, with about 35,000 remaining.[24]

    Description

    Clockwise from left: brown kiwi (Apteryx australis), little spotted kiwi (Apteryx owenii) and great spotted kiwi (Apteryx haastii) at Auckland War Memorial Museum
    1860s drawing of Apteryx, illustrating its distinctive features, including long beak, short legs and claws, and dark hair-like feathers.

    Their adaptation to a terrestrial life is extensive: like all the other ratites (ostrich, emu, rhea and cassowary), they have no keel on the sternum to anchor wing muscles. The vestigial wings are so small that they are invisible under the bristly, hair-like, two-branched feathers. While most adult birds have bones with hollow insides to minimise weight and make flight practicable, kiwi have marrow, like mammals and the young of other birds. With no constraints on weight due to flight requirements, brown kiwi females carry and lay a single egg that may weigh as much as 450 g (16 oz). Like most other ratites, they have no uropygial gland (preen gland). Their bill is long, pliable and sensitive to touch, and their eyes have a reduced pecten. Their feathers lack barbules and aftershafts, and they have large vibrissae around the gape. They have 13 flight feathers, no tail and a small pygostyle. Their gizzard is weak and their caecum is long and narrow.[25]

    The eye of the kiwi is the smallest relative to body mass in all avian species, resulting in the smallest visual field as well. The eye has small specialisations for a nocturnal lifestyle, but kiwi rely more heavily on their other senses (auditory, olfactory, and somatosensory system). The sight of the kiwi is so underdeveloped that blind specimens have been observed in nature, showing how little they rely on sight for survival and foraging. In an experiment, it was observed that one-third of a population of A. rowi in New Zealand under no environmental stress had ocular lesions in one or both eyes. The same experiment examined three specific specimens that showed complete blindness and found them to be in good physical standing outside of ocular abnormalities.[26] A 2018 study revealed that the kiwi’s closest relatives, the extinct elephant birds, also shared this trait despite their great size.[27]

    Unlike virtually every other palaeognath, which are generally small-brained by bird standards, kiwi have proportionally large encephalisation quotients. Hemisphere proportions are even similar to those of parrots and songbirds, though there is no evidence of similarly complex behaviour.[28]Duration: 38 seconds.0:38The call of a male North Island Brown Kiwi Apteryx mantelli

    Behaviour and ecology

    Before the arrival of humans in the 13th century or earlier, New Zealand’s only endemic mammals were three species of bat, and the ecological niches that in other parts of the world were filled by creatures as diverse as horses, wolves and mice were taken up by birds (and, to a lesser extent, reptiles, insects and gastropods).[29]

    The kiwi’s mostly nocturnal habits may be a result of habitat intrusion by predators, including humans. In areas of New Zealand where introduced predators have been removed, such as sanctuaries, kiwi are often seen in daylight. They prefer subtropical and temperate podocarp and beech forests, but they are being forced to adapt to different habitat, such as sub-alpine scrub, tussock grassland, and the mountains.[25] Kiwi have a highly developed sense of smell, unusual in a bird, and are the only birds with nostrils at the end of their long beaks. Kiwi eat small invertebrates, seeds, grubs, and many varieties of worms. They also may eat fruit, small crayfish, eels and amphibians. Because their nostrils are located at the end of their long beaks, kiwi can locate insects and worms underground using their keen sense of smell, without actually seeing or feeling them.[25] This sense of smell is due to a highly developed olfactory chamber and surrounding regions. It is a common belief that the kiwi relies solely on its sense of smell to catch prey but this has not been scientifically observed. Lab experiments have suggested that A. australis can rely on olfaction alone but is not consistent under natural conditions. Instead, the kiwi may rely on auditory and/or vibrotactile cues.[30]

    Relative size of the egg

    Once bonded, a male and female kiwi tend to live their entire lives as a monogamous couple. During the mating season, June to March, the pair call to each other at night, and meet in the nesting burrow every three days. These relationships may last for up to 20 years.[31] They are unusual among other birds in that, along with some raptors, they have a functioning pair of ovaries. (In most birds and in platypuses, the right ovary never matures, so that only the left is functional.[25][32][33])

    Kiwi eggs can weigh up to one-quarter the weight of the female. Usually, only one egg is laid per season. The kiwi lays one of the largest eggs in proportion to its size of any bird in the world,[34][a] so even though the kiwi is about the size of a domestic chicken, it is able to lay eggs that are about six times the size of a chicken’s egg.[37] The eggs are smooth in texture, and are ivory or greenish white.[38] The male incubates the egg, except for the great spotted kiwi, A. haastii, in which both parents are involved. The incubation period is 63–92 days.[25] Producing the huge egg places significant physiological stress on the female; for the thirty days it takes to grow the fully developed egg, the female must eat three times her normal amount of food. Two to three days before the egg is laid there is little space left inside the female for her stomach and she is forced to fast.[39]

    It was believed that the large eggs were a trait of much larger moa-like ancestors, and that kiwi retained large eggs as an evolutionarily neutral trait as they became smaller. However, research in the early 2010s suggested that kiwi were descended from smaller flighted birds that flew to New Zealand and Madagascar, where they gave rise to kiwi and elephant birds. The large egg is instead thought to be an adaptation for precocity, enabling kiwi chicks to hatch mobile and with yolk to sustain them for two and half weeks. The large eggs would be safe in New Zealand’s historical absence of egg-eating ground predators, while the mobile chicks would be able to evade chick-eating flying predators.[40]

    Lice in the genus Apterygon[41][42][43] and in the subgenus Rallicola (Aptericola)[44][45] are exclusively ectoparasites of kiwi species.[46]

    Status and conservation

    Traffic sign in New Zealand cautioning drivers of nearby kiwi

    Nationwide studies show that only around 5–10% of kiwi chicks survive to adulthood without management.[47][48] As of 2018 over 70% of kiwi populations are unmanaged.[49] However, in areas under active pest management, survival rates for North Island brown kiwi can be far higher. For example, prior to a joint 1080 poison operation undertaken by DOC and the Animal Health Board in Tongariro Forest in 2006, 32 kiwi chicks were radio-tagged. 57% of the radio-tagged chicks survived to adulthood.[citation needed]

    Efforts to protect kiwi have had some success, and in 2017 two species were downlisted from endangered to vulnerable by the IUCN.[50] In 2018 the Department of Conservation released its current Kiwi Conservation Plan.[49]

    Sanctuaries

    In 2000, the Department of Conservation set up five kiwi sanctuaries focused on developing methods to protect kiwi and to increase their numbers.[51]There are three kiwi sanctuaries in the North Island:

    and two in the South Island:

    A number of other mainland conservation islands and fenced sanctuaries have significant populations of kiwi, including:

    North Island brown kiwi were introduced to the Cape Sanctuary in Hawke’s Bay between 2008 and 2011, which in turn provided captive-raised chicks that were released back into Maungataniwha Native Forest.[66]

    Sanctuaries for kiwi are also referred to as ‘kōhanga sites’[61] from the Māori word for ‘nest’ or ‘nursery’.[67]

    The West Coast Wildlife Centre, at Franz Josef on the southern West Coast of New Zealand, is part of Project Nest Egg, breeding the vulnerable local species of kiwi known as the rowi.

    Operation Nest Egg

    Operation Nest Egg is a programme run by the BNZ Save the Kiwi Trust—a partnership between the Bank of New Zealand, the Department of Conservation and the Royal Forest and Bird Protection Society. Kiwi eggs and chicks are removed from the wild and hatched and/or raised in captivity until big enough to fend for themselves—usually when they weigh around 1200 grams (42 ounces). They are then returned to the wild. An Operation Nest Egg bird has a 65% chance of surviving to adulthood—compared to just 5% for wild-hatched and -raised chicks.[68] The tool is used on all kiwi species except little spotted kiwi.

    1080 poison

    Main article: 1080 usage in New Zealand

    In 2004, anti-1080 activist Phillip Anderton posed for the New Zealand media with a kiwi he claimed had been poisoned. An investigation revealed that Anderton lied to journalists and the public.[69] He had used a kiwi that had been caught in a possum trap. Extensive monitoring shows that kiwi are not at risk from the use of biodegradable 1080 poison.[70]

    Threats

    Introduced mammalian predators, namely stoats, dogs, ferrets, and cats, are the principal threats to kiwi. The biggest threat to kiwi chicks is stoats, while dogs are the biggest threat to adult kiwi.[48] Stoats are responsible for approximately half of kiwi chick deaths in many areas through New Zealand. Young kiwi chicks are vulnerable to stoat predation until they reach about 1–1.2 kg (2.2–2.6 lb) in weight, at which time they can usually defend themselves. Cats also to a lesser extent prey on kiwi chicks.[48] These predators can cause large and abrupt declines in populations. In particular, dogs find the distinctive strong scent of kiwi irresistible and easy to track, such that they can catch and kill kiwi in seconds. Motor vehicle strike is a threat to all kiwi where roads cross through their habitat. Badly set possum traps often kill or maim kiwi.[71]

    Habitat destruction is another major threat to kiwi; restricted distribution and small size of some kiwi populations increases their vulnerability to inbreeding.[48] Research has shown that the combined effect of predators and other mortality (accidents, etc.) results in less than 5% of kiwi chicks surviving to adulthood.[47]

    Relationship to humans

    Detail of the bottom edge of a kahu kiwi, showing the distinctive hair-like nature of the kiwi feathers.

    The Māori traditionally believed that kiwi were under the protection of Tāne Mahuta, god of the forest. They were used as food and their feathers were used for kahu kiwi—ceremonial cloaks.[72] Today, while kiwi feathers are still used, they are gathered from birds that die naturally, through road accidents, or predation, and from captive birds.[73] Kiwi are no longer hunted and some Māori consider themselves the birds’ guardians.[11]

    Scientific documentation

    In 1813, George Shaw named the genus Apteryx in his species description of the southern brown kiwi, which he called “the southern apteryx”. Captain Andrew Barclay of the ship Providence provided Shaw with the specimen. Shaw’s description was accompanied by two plates, engraved by Frederick Polydore Nodder; they were published in volume 24 of The Naturalist’s Miscellany.[74]

    Zoos

    In 1851, London Zoo became the first zoo to keep kiwi. The first captive breeding took place in 1945.[75] As of 2007 only 13 zoos outside New Zealand hold kiwi.[76] The Frankfurt Zoo has 12, the Berlin Zoo has seven, Walsrode Bird Park has one, the Avifauna Bird Park in the Netherlands has three, the San Diego Zoo has five, the San Diego Zoo Safari Park has one, the National Zoo in Washington, DC has eleven, the Smithsonian Conservation Biology Institute has one, and the Columbus Zoo and Aquarium has three.[77][78]

    In 2023, Zoo Miami apologized for mistreating a kiwi, after footage of visitors patting the nocturnal bird under bright lights caused outrage in New Zealand.[79]

    As a national symbol

    See also: National symbols of New Zealand

    The kiwi on an 1898 New Zealand stamp

    The kiwi as a symbol first appeared in the late 19th century in New Zealand regimental badges. It was later featured in the badges of the South Canterbury Battalion in 1886 and the Hastings Rifle Volunteers in 1887. Soon after, the kiwi appeared in many military badges; and in 1906, when Kiwi Shoe Polish was widely sold in the UK and the US, the symbol became more widely known.[80]

    During the First World War, the name “Kiwis” for New Zealand soldiers came into general use, and a giant kiwi (now known as the Bulford kiwi) was carved on the chalk hill above Sling Camp in England. Usage has become so widespread that all New Zealanders overseas and at home are now commonly referred to as “Kiwis“.[81]

    The kiwi has since become the best-known national symbol for New Zealand, and the bird is prominent in the coat of arms, crests and badges of many New Zealand cities, clubs and organisations. At the national level, the red silhouette of a kiwi is in the centre of the roundel of the Royal New Zealand Air Force.[38][82] The kiwi is featured in the logo of the New Zealand Rugby League, and the New Zealand national rugby league team are nicknamed the Kiwis.

    A kiwi has featured on the reverse side of three New Zealand coins: the one florin (two-shilling) coin from 1933 to 1966, the twenty-cent coin from 1967 to 1990, and the one-dollar coin since 1991. In currency trading the New Zealand dollar is often referred to as “the kiwi”.[83]

    A song, “Sticky Beak the Kiwi”, with words by Bob Edwards and music by Neil Roberts, was recorded in 1961, sung by Julie Nelson (aged 14) and accompanied by the Satins and the Don Bell Orchestra of Whangārei. A Christmas song, it portrays Sticky Beak as insisting on pulling Santa Claus’s sleigh when distributing presents south of the equator.[84]

    “How the Kiwi Lost its Wings” is a fable written by broadcaster Alwyn Owen in 1963. It uses elements of Māori mythology, such as Tāne Mahuta, and the World War I symbol of cowardice, white feathers, in a pourquoi story explaining features of New Zealand birds. Owen portrays the kiwi as nobly sacrificing its wings and flight in order to protect the trees from depredation by ground-dwelling creatures, and thereby winning its unique renown. Owen’s story is sometimes described as “A Maori Legend”.[85][86] It has been recorded as a children’s story,[87] published as a book,[88] was made into an animated film in 1980,[89] set to music for the Auckland Philharmonia Orchestra by Thomas Goss as “Tāne and the Kiwi” in 2002 (recorded for RNZ by Orchestra Wellington in 2008[90]), and performed as a ballet by the Royal New Zealand Ballet in 2022.[91]

  • KIWI

    KIWI

    Kiwifruit (often shortened to kiwi outside Australia and New Zealand), or Chinese gooseberry, is the edible berry of several species of woody vines in the genus Actinidia.[1][2] The most common cultivar group of kiwifruit (Actinidia deliciosa ‘Hayward’)[3] is oval, about the size of a large hen’s egg: 5–8 centimetres (2–3 inches) in length and 4.5–5.5 cm (1+3⁄4–2+1⁄4 in) in diameter. Kiwifruit has a thin, fuzzy, fibrous, tart but edible, light brown skin and light green or golden flesh with rows of tiny, black, edible seeds. The fruit has a soft texture with a sweet and unique flavour.

    Kiwifruit is native to central and eastern China.[1] The first recorded description of the kiwifruit dates to the 12th century during the Song dynasty.[4] In the early 20th century, cultivation of kiwifruit spread from China to New Zealand, where the first commercial plantings occurred.[1] The fruit became popular with British and American servicemen stationed in New Zealand during World War II. It later became commonly exported, first to Great Britain and then to California in the 1960s.[1][5]

    Etymology

    [edit]

    Early varieties were discovered and cultivated in China. They were described in a 1904 nursery catalogue as having “…edible fruits the size of walnuts, and the flavour of ripe gooseberries“,[6] leading to the name, Chinese gooseberry.[1]

    In the late 1950s, a major New Zealand exporter began calling it “kiwifruit” (Māori: huakiwi)[7] after being advised by a United States client that quarantine officials might mistakenly associate the unpopular name gooseberries[8] – which grow close to the ground – with suspicion of anthrax.[9] The name kiwifruit was adopted for the furry, brown fruit in relation to New Zealand’s furry, brown, national bird – the kiwi.[8] The name was first registered by Turners & Growers on 15 June 1959,[8] and commercially adopted in 1974.[1]

    In New Zealand and Australia, the word kiwi alone either refers to the bird or is used as a nickname for New Zealanders;[8] it is rarely used to refer to the fruit.[5][10] Kiwifruit has since become a common name for all commercially grown green kiwifruit from the genus Actinidia.[1] In the United States and Canada, the shortened name kiwi is commonly used when referring to the fruit.[11][12]

    History

    [edit]

    Further information: Kiwifruit industry in New Zealand

    Kiwifruit
    “Kiwifruit” in Traditional (top) and Simplified (bottom) Chinese characters
    Traditional Chinese獼猴桃
    Simplified Chinese猕猴桃
    Literal meaning“macaque peach”
    showTranscriptions

    Kiwifruit is native to central and eastern China.[1] The first recorded description of the kiwifruit dates to 12th century China during the Song dynasty.[4] As it was usually collected from the wild and consumed for medicinal purposes, the plant was rarely cultivated or bred.[13] Cultivation of kiwifruit spread from China in the early 20th century to New Zealand, where the first commercial plantings occurred.[1] After the Hayward variety was developed, the fruit became popular with British and American servicemen stationed in New Zealand during World War II. Kiwifruits were exported to Great Britain and then to California in the 1960s.[1][5]

    Close-up of Slice of Kiwifruit skin.

    In New Zealand during the 1940s and 1950s, the fruit became an agricultural commodity through the development of commercially viable cultivars, agricultural practices, shipping, storage, and marketing.[14]

    Species and cultivars

    [edit]

    Kiwifruit ‘Red Passion’ with a red-ring

    The genus Actinidia comprises around 60 species. Their fruits are quite variable, although most are easily recognised as kiwifruit because of their appearance and shape. The skin of the fruit varies in size, hairiness, and colour. The flesh varies in colour, juiciness, texture, and taste. Some fruits are unpalatable, while others taste considerably better than most commercial cultivars.[1][15]

    The most commonly sold kiwifruit is derived from A. deliciosa (fuzzy kiwifruit). Other species that are commonly eaten include A. chinensis (golden kiwifruit), A. coriacea (Chinese egg gooseberry), A. arguta (hardy kiwifruit), A. kolomikta (Arctic kiwifruit), A. melanandra (purple kiwifruit), A. polygama (silver vine) and A. purpurea (hearty red kiwifruit).[15]

    Fuzzy kiwifruit

    [edit]

    The larger A. deliciosa (fuzzy kiwifruit) at the rear compared to the smaller kiwi berry

    Most kiwifruit sold belongs to a few cultivars of A. deliciosa (fuzzy kiwifruit): ‘Hayward’, ‘Blake’ and ‘Saanichton 12’.[2] They have a fuzzy, dull brown skin and bright green flesh. The familiar cultivar ‘Hayward’ was developed by Hayward Wright in Avondale, New Zealand, around 1924.[15] It was initially grown in domestic gardens, but commercial planting began in the 1940s.

    ‘Hayward’ is the most commonly available cultivar in stores. It is a large, egg-shaped fruit with a sweet flavour. ‘Saanichton 12’, from British Columbia, is somewhat more rectangular than ‘Hayward’ and comparably sweet, but the inner core of the fruit can be tough. ‘Blake’ can self-pollinate, but has a smaller, more oval fruit, and the flavour is considered inferior.[2][15]

    Kiwi berries

    [edit]

    Kiwi berries are edible fruits the size of a large grape, similar to fuzzy kiwifruit in taste and internal appearance but with a thin, smooth green skin. They are primarily produced by three species: Actinidia arguta (hardy kiwi), A. kolomikta (Arctic kiwifruit) and A. polygama (silver vine). They are fast-growing, climbing vines, durable over their growing season. They are referred to as “kiwi berry, baby kiwi, dessert kiwi, grape kiwi, or cocktail kiwi”.[16]

    The cultivar ‘Issai’ is a hybrid of hardy kiwifruit and silver vine which can self-pollinate. Grown commercially because of its relatively large fruit, ‘Issai’ is less hardy than most hardy kiwifruit.[17][18]

    Actinidia chinensis

    [edit]

    Main article: Gold kiwifruit

    Golden kiwifruit Soreli

    Actinidia chinensis (yellow kiwi or golden kiwifruit) has smooth, bronze skin, with a beak shape at the stem attachment. Flesh colour varies from bright green to a clear, intense yellow. This species is ‘sweeter and more aromatic’ in flavour compared to A. deliciosa.[19] One of the most attractive varieties has a red ‘iris’ around the centre of the fruit and yellow flesh outside. The yellow fruit obtains a higher market price and, being less hairy than the fuzzy kiwifruit tastes better without peeling.[15]

    A commercially viable[20] variety of this red-ringed kiwifruit, patented as EnzaRed, is a cultivar of the Chinese hong yang variety.[21][22]

    ‘Hort16A’ is a golden kiwifruit cultivar marketed worldwide as Zespri Gold. This cultivar suffered significant losses in New Zealand in 2010–2013 due to the PSA bacterium.[23] A new cultivar of golden kiwifruit, Gold3, was found to be more disease-resistant and most growers have now changed to this cultivar.[24] ‘Gold3’, marketed by Zespri as SunGold is not quite as sweet as ‘Hort16A’,[25] and lacks its usually slightly pointed tip.

    Clones of the new variety SunGold have been used to develop orchards in China, resulting in partially successful legal efforts in China by Zespri to protect their intellectual property.[26] In 2021, Zespri estimated that around 5,000 hectares of Sungold orchards were being cultivated in China, mainly in the Sichuan province.[27]

    Cultivation

    [edit]

    Kiwifruit can be grown in most temperate climates with adequate summer heat. Where fuzzy kiwifruit (A. deliciosa) is not hardy, other species can be grown as substitutes.

    Breeding

    [edit]

    Kiwifruit growing on supported vine

    Often in commercial farming, different breeds are used for rootstock, fruit-bearing plants, and pollinators.[1] Therefore, the seeds produced are crossbreeds of their parents. Even if the same breeds are used for pollinators and fruit-bearing plants, there is no guarantee that the fruit will have the same quality as the parent. Additionally, seedlings take seven years before they flower, so determining whether the kiwifruit is fruit bearing or a pollinator is time-consuming.[28] Therefore, most kiwifruits, except rootstock and new cultivars, are propagated asexually.[28] This is done by grafting the fruit-producing plant onto rootstock grown from seedlings or, if the plant is desired to be a true cultivar, rootstock grown from cuttings of a mature plant.[28]

    Pollination

    [edit]

    Kiwifruit flowering

    Kiwifruit plants generally are dioecious, meaning a plant is either male or female. The male plants have flowers that produce pollen, the females receive the pollen to fertilise their ovules and grow fruit; most kiwifruit requires a male plant to pollinate the female plant. For a good yield of fruit, one male vine for every three to eight female vines is considered adequate.[1] Some varieties can self-pollinate, but even they produce a greater and more reliable yield when pollinated by male kiwifruit.[1] Cross-species pollination is often (but not always) successful as long as bloom times are synchronised.

    In nature, the species are pollinated by birds and native bumblebees, which visit the flowers for pollen, not nectar. The female flowers produce fake anthers with what appears to be pollen on the tips to attract the pollinators, although these fake anthers lack the DNA and food value of the male anthers.[29]

    Kiwifruit growers rely on honey bees, the principal ‘for-hire’ pollinator, but commercially grown kiwifruit is notoriously difficult to pollinate. The flowers are not very attractive to honey bees, partly because the flowers do not produce nectar and bees quickly learn to prefer flowers with nectar.

    Honey bees are inefficient cross-pollinators for kiwifruit because they practice “floral fidelity”. Each honey bee visits only a single type of flower in any foray and maybe only a few branches of a single plant. The pollen needed from a different plant (such as a male for a female kiwifruit) might never reach it were it not for the cross-pollination that principally occurs in the crowded colony; it is in the colonies that bees laden with different pollen cross paths.[30]

    To deal with these pollination challenges, some producers blow collected pollen over the female flowers.[29] Most common, though, is saturation pollination, in which the honey bee populations are made so large (by placing hives in the orchards at a concentration of about 8 hives per hectare) that bees are forced to use this flower because of intense competition for all flowers within flight distance.[1]

    Maturation and harvest

    [edit]

    Kiwifruit is picked by hand and commercially grown on sturdy support structures, as it can produce several tonnes per hectare, more than the rather weak vines can support. These are generally equipped with a watering system for irrigation and frost protection in the spring.

    Kiwifruit vines require vigorous pruning, similar to that of grapevines. Fruit is borne on ‘one-year-old and older’ canes, but production declines as each cane ages. Canes should be pruned off and replaced after their third year. In the northern hemisphere, the fruit ripens in November, while in the southern it ripens in May. Four-year-old plants can produce 15 tonnes of fruit per hectare (14,000 lb per acre) while eight-year-old plants can produce 20 tonnes (18,000 lb per acre). The plants produce their maximum at eight to ten years old. The seasonal yields are variable; a heavy crop on a vine one season generally comes with a light crop the following season.[1]

    Storage

    [edit]

    Fruit harvested when firm will ripen when stored properly for long periods. This allows fruit to be stored for up to 8 weeks after harvest.[1]

    Firm kiwifruits ripen after a few days to a week when stored at room temperature, but should not be kept in direct sunlight. Faster ripening occurs when placed in a paper bag with an apple, pear, or banana.[31] Once a kiwifruit is ripe, however, it is preserved optimally when stored far from other fruits, as it is sensitive to the ethylene gas they may emit, thereby tending to over-ripen even in the refrigerator.[31] If stored appropriately, ripe kiwifruit is normally kept for about one to two weeks.[31]

    Pests and diseases

    [edit]

    Pseudomonas syringae actinidiae (PSA) was first identified in Japan in the 1980s. This bacterial strain has been controlled and managed successfully in orchards in Asia. In 1992, it was found in northern Italy. In 2007/2008, economic losses were observed, as a more virulent strain became more dominant (PSA V).[32][33][34] In 2010 it was found in New Zealand’s Bay of Plenty Region kiwifruit orchards in the North Island.[35] The yellow-fleshed cultivars were particularly susceptible. New, resistant varieties were selected in research funded by the government and fruit growers so that the industry could continue.[36]

    Scientists reported they had worked out the strain of PSA affecting kiwifruit from New Zealand, Italy, and Chile originated in China.[37]

    Production

    [edit]

     China2,362,658
     New Zealand662,744
     Italy391,100
     Greece317,080
     Iran295,142
     Chile116,029
    World4,433,060
    Source: FAOSTAT of the United Nations[38]

    In 2023, world kiwifruit production was 4.4 million tonnes, led by China with 55% of the total (table). In China, kiwifruit is grown mainly in the mountainous area upstream of the Yangtze River, as well as Sichuan.[39] Other major producers were New Zealand and Italy (table).

    Production history

    [edit]

    Kiwifruit exports rapidly increased from the late 1960s to the early 1970s in New Zealand. By 1976, exports exceeded the amount consumed domestically.[40] Outside of Australasia, New Zealand kiwifruit are marketed under the brand-name label Zespri.[41] The general name, “Zespri”, has been used for the marketing of all cultivars of kiwifruit from New Zealand since 2012.[14][19]

    In the 1980s, many countries outside New Zealand grew and exported kiwifruit.[42] In Italy, the infrastructure and techniques required to support grape production were adapted to the kiwifruit. This, coupled with being close to the European kiwifruit market, led to Italians becoming the leading producer of kiwifruit in 1989. The growing season of Italian kiwifruit does not overlap much with New Zealand or the Chilean growing seasons, therefore direct competition between New Zealand and Chile was not a significant factor.[43]

    Much of the breeding to refine the green kiwifruit was undertaken by the Plant & Food Research Institute (formerly HortResearch) during the decades of ‘1970–1999’.[14] In 1990, the New Zealand Kiwifruit Marketing Board opened an office for Europe in Antwerp, Belgium.[14]

    Human consumption

    [edit]

    A pavlova with strawberries, passionfruit, kiwifruit and cream
    Nutritional value per 100 g (3.5 oz)
    Energy262 kJ (63 kcal)
    Carbohydrates15.8 g
    Sugars12.3 g
    Dietary fiber1.4 g
    Fat0.28 g
    Protein1.02 g
    showVitamins and minerals
    Other constituentsQuantity
    Water82 g
    Link to USDA FoodData Central entry
    †Percentages estimated using US recommendations for adults,[44] except for potassium, which is estimated based on expert recommendation from the National Academies.[45]
    Nutritional value per 100 g (3.5 oz)
    Energy255 kJ (61 kcal)
    Carbohydrates14.66 g
    Sugars8.99 g
    Dietary fiber3 g
    Fat0.52 g
    Protein1.14 g
    showVitamins and minerals
    Other constituentsQuantity
    Water83 g
    Link to USDA FoodData Central entry
    †Percentages estimated using US recommendations for adults,[44] except for potassium, which is estimated based on expert recommendation from the National Academies.[45]

    Kiwifruit may be eaten raw, made into juices, used in baked goods, prepared with meat, or used as a garnish.[1] The whole fruit, including the skin, is suitable for human consumption; however, the skin of the fuzzy varieties is often discarded due to its texture.[46] Sliced kiwifruit has long been used as a garnish atop whipped cream on pavlova, a meringue-based dessert. Traditionally in China, kiwifruit was not eaten for pleasure but was given as medicine to children to help them grow and to women who have given birth to help them recover.[1]

    Raw kiwifruit contains actinidain (also spelled actinidin) which is commercially useful as a meat tenderizer[47] and possibly as a digestive aid.[48] Actinidain also makes raw kiwifruit unsuitable for use in desserts containing milk or any other dairy products because the enzyme digests milk proteins. This applies to gelatin-based desserts since the actinidain will dissolve the proteins in gelatin, causing the dessert to either liquefy or prevent it from solidifying.

    Nutrition

    [edit]

    In a 100-gram (3.5 oz) amount, green kiwifruit provides 255 kilojoules (61 kilocalories) of food energy, is 83% water and 15% carbohydrates, with negligible protein and fat (table). It is particularly rich in vitamin C (103% DV) and vitamin K (34% DV), potassium, and has a moderate content of vitamin E (10% DV) and copper, with no other micronutrients in significant content. Gold kiwifruit has similar nutritional value to green kiwifruit, but contains higher vitamin C content (179% DV) and insignificant vitamin K content (table). Both types of kiwifruit are rich in dietary fiber.

    Kiwifruit seed oil contains on average 62% alpha-linolenic acid, an omega-3 fatty acid.[49] Kiwifruit pulp contains carotenoids, such as provitamin A beta-carotene,[50] lutein and zeaxanthin.[51]

    Allergies

    [edit]

    Allergy to kiwifruit was first described in 1981, and there have since been reports of the allergy presenting with numerous symptoms from localized oral allergy syndrome to life-threatening anaphylaxis.[52]

    The actinidain found in kiwifruit can be an allergen for some individuals, including children.[53][54][55] The most common symptoms are unpleasant itching and soreness of the mouth, with wheezing as the most common severe symptom; anaphylaxis may occur.