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Birds of prey

by  Gerard Hutching

New Zealand’s three native birds of prey are impressive hunters. The New Zealand falcon seizes other birds in mid-air, at speeds of up to 200 kilometres an hour. The swamp harrier circles high on thermal currents, looking for prey, and the morepork flies almost silently as it hunts in the night.


New Zealand’s birds of prey

Birds of prey are birds that hunt other birds and small animals. New Zealand has only three resident native birds of prey: the New Zealand falcon, the swamp harrier and the morepork.

The New Zealand falcon (Falco novaeseelandiae) and the swamp harrier (Circus approximans) are both daytime hunters. The morepork (Ninox novaeseelandiae) is a nocturnal hunting owl.

Since humans arrived in New Zealand, between 1250 and 1300 AD, several birds of prey have become extinct. The moa-hunting Haast’s eagle (Aquila moorei) was the world’s largest eagle, and had claws like a tiger’s. The large Eyles’s harrier (Circus eylesi), the laughing owl (Sceloglaux albifacies) and the New Zealand owlet-nightjar (Aegotheles novaezealandiae) are also extinct.

The German or little owl (Athene noctua) is not native. It was introduced early in the 20th century, and is common in eastern parts of the South Island and the Nelson region.

The barn owl is a rare vagrant from Australia that has bred in Northland.

Characteristics

The morepork, laughing owl and little owl are members of the owl order (Strigiformes), while falcons are Falconiformes and eagles and harriers are Accipitriformes. The three groups are not closely related, but share certain features. All hunt mostly from the air. They have acute vision, which helps them find prey. Some also have sensitive directional hearing. They have talons and curved bills for seizing prey – other birds, small mammals, lizards, frogs, and insects.

Super size predator

Haast’s eagle, now extinct, was the world’s largest eagle. Weighing around 12 kilos, it preyed on big birds, including 200-kilo moa, and died out when these were hunted to extinction. Haast’s eagle had humble origins. Its closest relatives are among the world’s smallest eagles, including Australia’s little eagle (Aquila morphnoides), which weighs just 1 kilo.

Other avian predators

Some other birds are at least partly predatory, even if they are not considered to be birds of prey. Many eat insects, worms, snails, frogs, lizards or small fish. Kea (Nestor notabilis), native mountain parrots, sometimes attack seabird chicks in their burrows. Weka (flightless rails, Gallirallus australis) take bird eggs and chicks from nests. So do black-backed gulls (Larus dominicanus), skuas (Catharacta lonnbergi) and non-native magpies (Gymnorhina tibicen). The 18-kilogram flightless adzebill (Aptornis defosser and A. otidformis), now extinct, apparently hunted other birds. All sea birds are marine predators – they catch and eat marine animals.


Morepork: New Zealand’s native owl

At dusk, the melancholy sound of the morepork (Ninox novaeseelandiae) can be heard in forests and parks as it calls to other moreporks and claims territory. Its European name (morepork), Māori name (ruru) and Australian name (boobook) all echo its two-part cry.

The morepork is New Zealand’s only surviving native owl. They are found in mainland New Zealand’s forests and on many offshore islands. They are less common in the drier, more open regions of Canterbury and Otago. Speckled dark brown, with yellow eyes and long tails, they are around 29 centimetres long from head to tail and 175 grams in weight. Another morepork subspecies lives on Norfolk Island. It was reduced in numbers to a single female, but after two males were introduced from New Zealand in 1987, a hybrid population was re-established.

The larger laughing owl became extinct in the 20th century. The German or little owl is a smaller introduced species.

Neighbourhood watch

Birds such as robins, grey warblers and fantails can end up as prey for moreporks. During the day, these small birds sometimes mob drowsy moreporks and chase them away from their roosts. Their noisy mobbing calls force the sleepy predators to search for a more peaceful spot.

Habits

During the day, moreporks sleep in roosts. By night they hunt a variety of animals – mainly large invertebrates including scarab and huhu beetles, moths and caterpillars, wētā and spiders. They also take small birds, rats and mice. They can find suitable food in pine forests as well as native forest.

Stealthy fliers

Moreporks have soft fringes on the edge of their feathers, so they can fly almost silently and not alert potential prey. This also allows moreporks to hear the movements of their prey as they approach, rather than the noise of their own wings. They have acute hearing and their large eyes are very sensitive to light.

Able hunters

A morepork uses its sharp talons to catch or stun its prey, which it carries in its bill. Moreporks are canny hunters, as observed by ornithologist David Mudge:

I watched one pair visit the nests of three hapless starlings who had made the mistake of nesting in the same tree as the owls. The moreporks would go from one starling’s nest to the next, hovering outside and reaching in with their talons, feeling for young birds to grab. I have seen a pair of moreporks ferry seven chicks back to their nest in 15 minutes. 1

Breeding

Moreporks nest in tree hollows, in clumps of epiphytes (perching plants), or in cavities among rocks and roots. The female lays up to three white eggs, usually between October and November, which she incubates for 20 to 30 days. During this time she rarely hunts, and the male brings food to her. Once the chicks hatch she stays mainly on the nest until the young owls are fully feathered. They can fly at about 35 days.

Ungracious hosts

Scientists trying to establish a population of rare shore plovers on Motuora Island in the Hauraki Gulf were mystified as to why only two birds survived out of 75 placed there. The culprits turned out to be five pairs of moreporks that ate or chased away the new arrivals.

Māori associations

In Māori tradition, the morepork or ruru was often seen as a watchful guardian. As a bird of the night, it was associated with the spirit world. Its occasional high, piercing call signified bad news, such as a death, but the more common ‘ruru’ call heralded good news.

A number of sayings referred to the birds’ alertness. One saying warned an enemy that they were being watched:

Etia anō āku mata me te mata-ā-ruru e tīwai ana
Me te mata kāhu e paro noa rā kai te tahora!
My eyes are like morepork eyes turning from side to side,
Like the eyes of a hawk who soars over the plain! 2
Footnotes
    • Quoted in Geoff Moon, ‘Morepork’, New Zealand Geographic 32 (Oct–Dec 1996), p. 93. › Back
    • Margaret Orbell, Birds of Aotearoa. Auckland: Reed, 2003, p. 101. › Back

New Zealand falcon

Swooping down on their prey at speeds of up to 200 kilometres per hour, New Zealand falcons are supreme aerial hunters. The falcon (kārearea, Falco novaeseelandiae) almost always takes live prey on the wing, catching it with sharp talons. The fearless bird will attack and kill animals larger than itself.

Habitat and distribution

New Zealand falcons vary in size and colour according to their main habitat. The bush falcon (whose population is an estimated 650 pairs) is found in the North Island and the west and north-west South Island. The South Island’s eastern falcon (3,150 pairs) is found in open country. It is larger, and paler in colour. The southern falcon (200 pairs) lives in coastal Fiordland and the Auckland Islands, and has more reddish plumage.

These population figures are from a 1978 study, but numbers have probably fallen since. The World Conservation Union classifies the falcon as a near-threatened species. It is threatened by introduced predators such as stoats, by changes in habitat, and by people who shoot it illegally.

Hunting techniques

New Zealand falcons are not big birds, so their hunting feats are all the more impressive. At 500 grams and 45 centimetres, the female is larger than the male (300 grams). Females can kill young rabbits or hares weighing up to 3 kilograms.

Falcons also take large birds such as white-faced herons, kererū (New Zealand pigeons), ducks and pheasants. They catch big insects such as grasshoppers and beetles.

Falcons’ wings are angled back like an arrow. An attacking falcon dives steeply, giving what ornithologist Walter Buller described as a ‘shrill cry of terror’ when it seizes its victim. After it catches a bird, it takes it to a plucking post, and dislocates the bird’s neck using a special notched tooth that all falcons have. It then plucks the feathers and eats the entire bird.

Courtship and breeding

Food plays an important role in falcon courtship. The courtship starts in early spring, when the male chases the female and pretends to attack her. This is followed by aerial acrobatics. The bond is sealed when the male carries prey to the female. She chases him, and he offers her the food near their future nest site.

Between September and December the female lays up to four reddish brown eggs. Falcons nest in a simple scraped hollow on a sheltered cliff ledge, in an astelia epiphyte high in a tree, or on the ground under a log or bush. They fiercely defend the surrounding area, and may dive-bomb passers-by. Male and female both incubate the eggs, for 33–35 days in total. Juvenile falcons can fly at around 35 days and may be independent of their parents after three months.

Friends of the vine

Marlborough wine growers are hoping that falcons will help rid their vineyards of pest birds that eat or damage grapes. The growers are supporting a breeding programme to re-establish the falcons among vineyards on the Wairau Plains.

Conserving falcons

Groups including the Wingspan Birds of Prey Trust, the Raptor Association of New Zealand and the Department of Conservation are joining forces to save falcons. They have raised falcons in captivity and released them into the wild.


Swamp harrier

The swamp harrier (Circus approximans), also known as the kāhu, harrier hawk or Australasian harrier, is a bird of the open country. It is often seen soaring and looking for prey, or eating dead rabbits or possums on the road.

The swamp harrier also occurs in Australia, New Guinea and many islands of the southern Pacific. In New Zealand harriers are found from the Kermadec Islands in the far north, to the Chatham Islands, and they occasionally stray as far as the chilly subantarctic islands.

Fossil records show that it came across the Tasman Sea from Australia, and became established in New Zealand less than 1,000 years ago. At that time Eyles’s harrier (Circus eylesi), four times larger, was also present.

At 850 grams, fully grown females are 200 grams heavier than males. Both sexes are the same length, about 55 centimetres. The oldest known age for a harrier in New Zealand is 18 years.

Habitat and food

Swamp harriers hunt in open country. After Europeans arrived in New Zealand and cleared land for farming, the birds’ numbers increased. They catch small birds and mammals up to the size of rabbits, as well as lizards, frogs, fish and large insects. They also eat carrion, including road kill and dead lambs, and spend much time hunting for birds' nests. Since the 1950s, successful rabbit control has meant less food for harriers, and their numbers have fallen.

Aerial hunter

The harrier is an adept hunter when flying, as ornithologist Edgar F. Stead observed:

One day I watched a Harrier beating over a stubble field, when it flushed a Skylark, which flew away some distance and settled. The Harrier carefully marked the spot, and flew swift and low towards it; saw the Lark, and struck at it on the ground. The Lark dodged the blow, ducked out from beneath the Hawk, and settled again about two yards away; but the Hawk, with a rapidity of movement with which one could scarcely have credited it, rose and swept back on its victim and flew off with it in its talons. 1

When looking for food, harriers hold their large straight wings in a shallow V to soar on thermal winds, circling effortlessly until they dive for prey. In their courtship ritual, the male performs steep dives and loops, and the female turns on her back in mid-air to greet him.

Breeding

The breeding season starts in June, when males establish territories of several square kilometres. Females build nests in tall grass-like plants such as toetoe. They usually lay three to five off-white eggs between September and December. The male does not feed the chicks, but delivers food to his mate while both are flying. Chicks are able to leave the nest at 45 days.

Signs of age

Māori knew older harriers as kāhu-kōrako, a reference to their pale feathers. As harriers grow older, they lose the dark plumage of youth, and some very old birds appear almost grey.

Hunting harriers

Believing harriers posed a threat to introduced game birds such as partridges, pheasant and quail, Acclimatisation Societies offered a bounty until the 1940s. Hundreds of thousands were killed between 1860 and 1950. Naturalist Walter Buller reported that ‘upwards of a thousand’ were killed each year on one Canterbury sheep run – yet they remained abundant.

The harrier has been protected by law since 1986.

Māori tradition

To Māori, the harrier was a symbol of victory and chieftainship. Its effortless flight inspired a chant used by East Coast Māori when performing a difficult task like moving a heavy log:

Te kāhu i runga whakaaorangi ana e rā,
Te pērā koia tōku rite, inawa ē!
The hawk up above moves like clouds in the sky.
Let me do the same! 2
Footnotes
    • Edgar F. Stead, The life histories of New Zealand birds. London: Search, 1932, p. 111. › Back
    • Margaret Orbell, The natural world of the Maori. Auckland: David Bateman, 1985, p. 114. › Back

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How to cite this page: Gerard Hutching, 'Birds of prey', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/en/birds-of-prey/print (accessed 27 June 2017)

Story by Gerard Hutching, published 24 Sep 2007, reviewed & revised 17 Feb 2015