Land birds are those that live in forests, scrub and open country. The term does not include birds of wetland, shore or sea.
Many of New Zealand’s land birds are strange and unusual. They include a flightless, nocturnal parrot – the kākāpō (Strigops habroptilus), and the almost wingless kiwi (Apteryx species). The kiwi has feathers like stiff hair, an immensely long bill and strong legs. Others have joined it in giving up flight, and growing large. Some live more like browsing mammals than birds.
Other remarkable birds once roamed the land and skies, such as the biggest moa species, weighing 270 kilograms, and its predator Haast’s eagle (Aquila moorei), the world’s largest eagle.
Very few New Zealand land birds are brightly coloured, although many have subtle patterns and sheens. Even parrots and parakeets, which are brightly coloured in the rest of the world, are mainly plain green, although the kea (Nestor notabilis) and kākā (Nestor meridionalis) have brilliant red underwings.
The endemic South Island takahē (Porphyrio hochstetteri) is more colourful than its swamp hen relatives elsewhere. It has turquoise, navy and olive-green plumage and a crayfish-red bill and legs.
From a distance, the tūī (Prosthemadera novaeseelandiae) appears plain black, apart from tufts of white feathers on its throat, but its plumage can take on a green and blue iridescent sheen, with lacy grey filaments around the shoulders.
The wattlebird species have blue, orange or red wattles at the base of the bill.
The bills of male and female huia were very different. The male of this extinct species had a stout, adze-like bill. The female’s was long, slender and down-curved. The story goes that the pair would forage for food together, he tearing into rotting wood and she using her ‘forceps’ to extract huhu and other large grubs. But was it true? The specimens locked in museum cases will never tell.
Some flightless birds have rotund bodies, particularly the leaf-eaters such as the takahē and kākāpō that carry lots of slowly digesting material. Many, including the kiwi, have stocky, strong legs. For flightless birds large size was no great drawback, and a long neck like a giraffe’s allowed the biggest moa (Dinornis species) to reach leaves up to 2 metres above the ground.
Ducks and geese are usually wetland birds, but in New Zealand some of them seldom, or never, set foot in water. The most terrestrial (land-based) of these were the huge South Island goose (Cnemiornis calcitrans) and slightly smaller North Island goose (C. gracilis), which are now extinct. The South Island goose stood 1 metre tall and weighed around 18 kilograms. Also extinct is the Finsch's duck (Chenonetta finschi), which was abundant and completely terrestrial.
The paradise shelduck (pūtangitangi, Tadorna variegata) spends about as much time ashore as on the water. Before mammalian predators were introduced, the brown teal (pāteke, Anas chlorotis) was probably more terrestrial than the few that survive today.
Only 91 of New Zealand’s 252 native birds are land birds. (These numbers include recently extinct species.) The rest are wetland birds, shore birds or seabirds. This is unusual, as 90% of the world’s birds are land birds.
Part of the reason for New Zealand having a smaller proportion of land species is the country’s extensive wetlands, long shoreline, and vast marine area – ideal habitats for birds of shore and sea. Another factor is that 2,000 kilometres of water separate modern-day New Zealand from its nearest large neighbour. Land birds are less likely to fly long distances across water than the other groups.
About half the world’s bird species belong to one order, Passeriformes. These are passerines (sometimes called the perching birds), and include sparrows and blackbirds. New Zealand has 49 native passerine species, with nine found only on outer islands.
Native passerines include some of the world’s oldest – the rifleman and rock wren (Acanthisittidae family), and the wattlebirds (Callaeidae family). Other passerines include the whitehead (Mohoua albicilla), robins (Petroica species), the tūī, and the recently extinct piopio (Turnagra capensis and T. tanagra).
New Zealand’s land bird fauna is unusual and restricted. This is in part because of where they came from, and how long ago they or their ancestors arrived. Another factor is that certain other animal groups that are common elsewhere did not reach New Zealand.
Most of New Zealand’s land birds’ ancestors can be traced back to two sources:
The first group includes the most unusual bird groups – the wren and maybe the wattlebird families, and the endemic parrot family Strigopidae, which includes kākāpō, kākā and kea.
These birds evolved in ancient forests at the time of the dinosaurs. While mammals were evolving elsewhere, New Zealand bird species remained isolated. With no land mammals apart from bats, and no predatory snakes, the birds could evolve in unique ways. In particular, they had less need to fly as an escape strategy, and could safely feed on the ground.
The ancestors of the second group were apparently blown across the Tasman Sea from Australia. Some came via New Caledonia. They include:
All of these except the fantail have been in New Zealand long enough to evolve quite differently from their Australian ancestors – weka and takahē became flightless.
Over the millennia, land bird species arrived from Australia from time to time, carried by strong westerly winds. Relatively few became established, possibly because they were ill-adapted to their new habitat. But as humans cleared large areas of land, more self-introduced Australian species became well established. These included the silvereye (whose Māori name, tauhou, means stranger) and the welcome swallow (Hirundo neoxena).
A few species came from other places, while the origins of others remain unclear. There has even been debate over the origin of the kiwi. Some scientists maintained its ancestors were on New Zealand when it split from Gondwana, and others suggested it was an early arrival from Australia. In 2015 DNA research showed that the kiwi's closest relative was the extinct giant elephant bird, Mullerornis agilis, from Madagascar.
New Zealand’s recently extinct Haast’s eagle was the world’s largest eagle. With claws like a tiger’s, it attacked and killed large birds, including the giant moa. Weighing 12 kilograms, it had a 3-metre wing span. Its closest relatives include Australia’s little eagle (Aquila morphnoides), which weighs just 1 kilogram. They all shared a common Australian ancestor about a million years ago, showing how quickly a new environment can shape the evolution of a species.
Eighty-five of New Zealand’s 91 species of native land birds are endemic (they occur nowhere else). In comparison, the British Isles has just one endemic species. Only remote oceanic islands such as Hawaii have a similarly high proportion of endemic land birds.
Some of these endemic species belong to entire families or orders that are endemic to New Zealand. This means that even their nearest relatives in other countries are only very distantly related. Few countries have such a high number of endemic families or orders.
All birds are descended from birds that could fly. However, over half of New Zealand’s native land birds became flightless, had reduced powers of flight (such as the kōkako and saddleback), or flew reluctantly. Some, such as the moa, kiwi, takahē and kākāpō, are well known. Also noteworthy is that of the world’s four known species of flightless passerine birds (perching birds), three were New Zealand wrens. The other three native wrens can fly short distances.
The little New Zealand wrens are the most primitive living passerines (perching birds). The three flightless species are now extinct. So is the flighted bush wren. Two species survive. The rifleman or tītiti pounamu is New Zealand’s smallest bird, weighing just 7 grams. The rock wren is a little alpine bird that lives under rocks beneath winter snows.
For birds that live among mammals, flight is an advantage for two reasons. Firstly, some mammals are effective predators, and flight is a convenient way to escape. Secondly, they compete with mammals for food. Some mammals, such as possums, can climb trees, but most eat a range of foods at ground level – whether they are browsers or predators. Flight enables birds to specialise in foods beyond the reach of most mammals, and to stay out of reach themselves.
Before humans reached New Zealand, the country had no predatory land mammals. The main predators were birds – eagles, falcons, harriers and owls. Flying was therefore risky for other birds. More effective strategies to avoid being caught were camouflaged plumage, feeding at night, seeking cover and staying motionless.
The ability to fly was no great advantage, and had considerable costs. Flying uses more energy than walking, requiring more high-energy food. Also, the extra muscles and skeletal structures needed for flight account for nearly a quarter of a bird’s body weight. If a bird could find all the food it needed close at hand, and flying was not necessary to escape predators, then flight became an expensive luxury.
The majority of the world’s flightless birds evolved on mammal-free islands, and their extinction was mainly caused by people and introduced predatory mammals. When rats, stoats and human hunters reached New Zealand, some of the most interesting and unusual birds could not survive.
Most New Zealand flightless land birds belong to one of two groups, according to how they find food. Birds in both groups could safely eat low-growing vegetation, or prey in soil or leaf litter, without having to fly away.
Kiwi, snipe (tutukiwi, Coenocorypha species), weka and flightless wrens eat ground-dwelling prey – worms and larvae in soil, bugs in leaf litter – that is available year-round. In other countries, flighted birds also take this prey, but they fly to escape predatory mammals.
The birds in the other group of ground-dwelling birds are herbivorous – they eat leaves, which do not provide enough energy for flying. Leaves are also hard to digest, so these birds need a longer and heavier digestive tract, and tend to be larger than those that eat more nutritious foods. They included the 2–3-kilogram kākāpō and takahē, the huge North and South Island geese, and nine species of moa, including the giant moa (Dinornis giganteus) that weighed up to 270 kilograms.
The tree-dwelling kōkako and kererū also eat leaves. Kōkako also eat some other foods, and have limited powers of flight. Kererū have full flight, and gain their extra energy from the more nutritious parts of the plant such as fruits and buds.
In most of the world, it is mainly land mammals that browse and graze. But in New Zealand, where the only land mammals were bats, some birds became ground-dwelling, flightless and plant-eating. Each species within this ecological guild (animal group with related ecological niches) ate a particular range of foods. These browsing birds were the equivalent of kangaroos and possums in Australia, or the giraffes, elephants and other plant-eating mammals of Africa.
Today there is fierce competition for these foods from many introduced mammals including rats, wild pigs, feral goats and deer, and large areas of forest have become farmland.
Most of New Zealand’s land birds have become extinct within the last few decades or centuries, or are classified as threatened or endangered. Because most are long-lived and reproduce at a low rate, slowly declining populations may eventually become extinct.
Forty land bird species have become extinct, and the Department of Conservation classifies 37 of the 51 living species as threatened.
Many land birds, including the saddleback or tīeke (Philesturnus rufusater and P. carunculatus) and the stitchbird or hihi (Notiomystis cincta), became extinct on the mainland. They survived only on a few small islands free from mammalian predators.
Some, such as the kākāpō, little spotted kiwi and black robin, are true refugees. They have been deliberately moved to island sanctuaries as part of conservation efforts, and would otherwise be extinct. Many of these islands are off-limits to the general public. Their ecosystems are fragile and the risk of introducing rats and other pests is too great to allow visitors.
New Zealand snipe or tutukiwi are flightless from day to day. But occasionally, males fly high then plunge downwards so fast that the air vibrates their tail feathers, producing a mysterious roaring noise. They do this mainly on moonlit nights, and the purpose of these aerial displays is unknown. By avoiding flight at other times they are safer from harrier or skua attack, but staying on the ground puts them at risk from rats.
The main threats to native land birds are the mammals that were introduced when people settled the land. The land birds’ strategies for avoiding predatory birds made them all the more vulnerable to predatory mammals. For example, when threatened, the New Zealand snipe flies just a few metres, seeks cover, and then remains stock still, relying on its plumage for camouflage. This keeps it hidden from birds of prey that hunt by sight, but not from mammals following a scent.
Losses began with the introduction of the Pacific rat or kiore (Rattus exulans) that arrived with Polynesian settlers about 750 years ago. The fast-breeding rats swarmed across the countryside, devouring small ground-dwelling birds and the eggs of ground-nesting birds.
Humans drove the large land birds, including all moa species, adzebills (Aptornis otidiformis and A. defosser), land geese and Finsch’s duck (Chenonetta finschi) to extinction. Relatively easy to hunt, these flightless birds were a staple food for early Māori until none remained.
A second wave of extinctions began in 1769 when European voyagers and then settlers introduced two larger species of rats (Rattus norvegicus, R. rattus), cats (Felis catus), stoats (Mustela nivalis), ferrets (M. furo), possums (Trichosurus vulpecula) and other predators. Birds that had evolved in the absence of mammalian predators simply stood no chance.
Competition from mammals such as possums and deer reduces the food available for kōkako, takahē and other endemic birds. Competition from humans, who have taken land to produce food, has led to widespread and rapid loss of wetlands and forests. Over 90% of New Zealand’s wetlands and two-thirds of its forests have been lost since the first human settlement, much of it in the last 180 years. While a lot of forest remains, most of it is at high altitudes or in the wetter western parts of the country. Meanwhile the dry lowland forests of eastern New Zealand, once biologically diverse, have essentially disappeared.
Endemic species are more vulnerable than other native species. Particularly at risk are those that belong to families or orders found only in New Zealand (the most distinctive and unusual species). Nearly all of these are threatened, endangered or extinct. New Zealand has lost many of its unique taonga, and is in danger of losing more.
New Zealand is unusual in that most of the birds in the cities, towns and farmlands have been brought from some other part of the world. In comparison, most of the birds in Australia or any European or American country are native, even in the largest cities.
The Pākehā settlers who came to New Zealand enthusiastically brought many plant and animal species. Acclimatisation Societies were formed to introduce useful or ornamental animals, birds, fish and plants.
Most introduced species came with settlers from Britain, but a few have been brought from elsewhere. Among the land birds the magpie (Gymnorhina tibicen) was introduced from Australia, the California quail (Callipepla californica) from the USA, and the chukor (Alectoris chukar) and common myna (Acridotheres tristis) from Asia.
Today the most common and widespread land birds in towns and farmland, including house sparrows, blackbirds, starlings and various finches, are introduced.
The common silvereye and welcome swallow have colonised New Zealand since Pākehā settlement created habitats that suited them. These are considered native because they arrived unassisted.
Introduced species are far less common in indigenous forests, where native birds prevail. On mammal-free islands with relatively intact native forest habitats, silvereyes, swallows and introduced species are rare. Because the native and introduced birds are adapted to such different habitats, introduced birds have apparently had little direct effect on the native species.
Zealandia (previously Karori Sanctuary) in Wellington has a 250-hectare pest-free reserve bounded by a high fence that keeps out all introduced mammals except mice. Native birds have increased their numbers and endangered species such as little spotted kiwi, saddlebacks, stitchbirds and kākā have been released there.
Only a handful of native land birds can survive in towns and cities. Even on farmland few remain unless large enough remnants of native forest or scrubland are saved. The fantail, silvereye, grey warbler, bellbird, tūī and kererū are the most adaptable native land birds. At least some of these species are in towns and on farmland where there are still suitable introduced or native tree areas and food sources. They will also return to areas where native bush is replanted.
Why are so few native land birds found in towns and farms? They evolved in unique forest habitats that were very different from today’s urban and rural environments. They were ill-adapted to cope with the dramatic habitat changes, including the rats and cats that are so numerous where people live.
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