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Gulls, terns and skuas

by  Gerard Hutching

The screeching and scavenging gulls so familiar around New Zealand’s coastlines are closely related to terns and skuas. This group includes the small, delicate fairy terns as well as aggressive, cannibalistic skuas.


Black-backed gulls

Gulls, terns and skuas

Gulls, terns and skuas belong to the order Charadriiformes, which includes both sea and shorebirds. They have webbed feet and are partly dependent on marine or freshwater food sources. In New Zealand all of these birds are protected, except black-backed gulls. Subantarctic skuas are partially protected.

Gulls and terns are gregarious birds common to New Zealand’s inland and coastal regions. Subantarctic skuas are found on the Chatham Islands and on islands south of the mainland.

Bird calls

Gulls in New Zealand slang have a rough reputation. In the 1930s wharf labourers waiting for scraps of work were called seagulls. And in rugby, a seagull is a loose forward who scavenges for pickings on the edges of tight play.

Black-backed gulls

Black-backed gulls or karoro (Larus dominicanus) can be found in the southern hemisphere from Antarctica to the subtropics. Elsewhere they are known as Dominican or kelp gulls. The subspecies in New Zealand is the widespread Larus dominicanus dominicanus. There are probably over two million in coastal and near-shore environments, and inland waterways. They do not generally venture far out to sea.

Of New Zealand’s gull species, black-blacked gulls are the largest, at 60 centimetres long. Males weigh over 1 kilogram, and females about 850 grams. Adults have white bodies, black wings, and yellow bills and legs. Juveniles look very different, with mottled brown plumage and black bills and legs.

Predators

The gulls threaten rare birds such as the New Zealand dotterel, and some terns and petrels by preying on eggs and chicks. They can also attack newborn lambs. They were found to spread Salmonella brandenburg, an infection causing spontaneous abortions in sheep and cattle, which the gulls got by eating dead foetuses with the disease.

Black-backed gulls also feed on fish, shellfish, offal and carcasses, and fruit. They are often seen in ploughed fields taking worms and grubs. The gulls often return to favourite feeding spots.

Training and taming

Black-backed gulls’ predatory nature has been put to good use. Māori trained them to eat the caterpillars that infested kūmara (sweet potatoes). Some birds became tame enough to follow people around, while others had their wings clipped to stop them flying away.

Breeding and life span

Black-backed gulls generally breed in large colonies, anywhere from coastal sites to mountain lakes. They make nests of plant material, and lay one to three greyish-green eggs in October–November, which both sexes incubate. Chicks fly when they are 50 days old, and the birds breed from the age of four. They usually live for 14 years, but can live twice as long.


Red- and black-billed gulls

Red-billed gulls

The red-billed gull or tarāpunga (Larus novaehollandiae) has a white body with grey wings tipped with black then white. Their bills and legs are red when they are adult. They are 37 centimetres long – considerably smaller than black-backed gulls. Males weigh 300 grams and females about 260 grams.

There are several subspecies, of which Larus novaehollandiae scopulinus occurs only in New Zealand. Red-billed gulls are known as silver gulls in Australia and New Caledonia.

Gulls of Mokoia

In 1823 the Ngāpuhi tribe attacked the Te Arawa people living on Mokoia Island, in Lake Rotorua. Te Arawa only knew of the imminent attack when a flock of red- and black-billed gulls flew up, screaming a warning. The gulls circled overhead while Te Arawa were defeated. Following the battle, the Te Arawa priests honoured the birds by declaring them tapu (sacred).

The gulls are mainly coastal and offshore island birds, with the exception of a few at Lake Rotorua in the North Island. Here they nest alongside black-billed gulls, and occasionally interbreed.

The largest colonies were at Kaikōura Peninsula and on outlying islands, but numbers have declined catastrophically because of a diminishing food supply. In 2014 Otago populations of the gulls were increasing.

Since the 1960s studies of red-billed gulls on Kaikōura Peninsula have documented their habits and social organisation. 

The gulls breed from October to December, laying one to three brownish eggs with purple blotches. Both sexes incubate the eggs, and the young fledge at 37 days. Once the breeding season is over, the colony disperses, and Kaikōura gulls have been seen as far afield as Auckland and Invercargill. Female gulls live around nine years and males about six, but some live up to 25 years.

Black-billed gulls

Of New Zealand’s three species of gull, the black-billed gull (Larus bulleri) is the only endemic gull. Similar in size to red-billed gulls, their bills are black, and they are longer and finer in shape, with reddish-black legs and paler wings.

Black-billed gulls eat small fish, whitebait and flatfish, and take earthworms and grass grubs from pastureland. They also feed on the wing, taking cicadas, moths and aquatic insects. In winter they fly to estuaries and harbours to eat marine invertebrates and shellfish, or to parks for worms and human handouts.

Black-billed gulls mainly breed inland, beside South Island rivers. In the late 20th century their breeding habitat became more varied, and some were breeding at Kaipara and Manukau harbours. They nest in colonies, and make nest mounds of dry grass and twigs on shingle. They lay one to four pale green-grey eggs from September to December, and parents share incubation.

Chicks are left alone within a day of hatching, and parents return to feed them by regurgitating food onto the ground. Fledglings leave the nest when they are 26 days old. The birds live about 18 years.

Despite extending their range, black-billed gulls are declining in number. Populations have dropped along Canterbury and North Otago rivers, where hydroelectric schemes and irrigation have affected all bird species which nest there. Even in Southland, where 78% of the gulls nest, populations are falling. In 1974 there were 84,900 gulls breeding along the Oreti River; in 1997 there were 15,308. A New Zealand-wide count in 1996 found 48,000 nests.


Black-fronted terns

Terns

Terns belong to the Sternidae family. They are distinguishable from gulls by a fork-like tail, which has led to their popular name of sea swallow. At breeding time their plumage changes and their cap becomes deep black. After breeding the black fades and the colours of the bill become less intense.

Six species of tern breed in New Zealand, while several others are regular or rare visitors. Four tropical or subtropical members of the family, called noddies, breed on the northern Kermadec Islands.

Black-fronted terns

The black-fronted tern or tarapirohe (Chlidonias albostriatus) occurs only in New Zealand. It is the one tern that only breeds inland.

Black-fronted terns are small – 29 centimetres long and 80 grams in weight. They have white cheek bands, a red bill and white body with grey wings. Their forked tail is pale grey, and their rump is white.

They breed from September to January, laying one to four dark eggs with brown blotches in a shallow scrape on shingle. Like all of New Zealand’s terns, both sexes incubate the eggs. The young fledge at 30 days.

Known as ploughboys or the ploughman’s friend, black-fronted terns feed on grubs and worms from freshly dug earth. Along rivers and streams they eat mayflies, stoneflies, skinks and small fish. Once summer is over, the terns leave their nesting grounds for coastal and inshore areas from Stewart Island to the southern North Island, where they feed mainly on crustaceans in the plankton.

Some black-fronted terns live along the braided rivers of the South Island, and like other birds there, are under threat from hydroelectric development, predators and rampant weeds, which smother nest sites. Around 60% of New Zealand’s 5,000-strong population lives in the upper Waitaki River basin, where in 1991 a recovery project was launched to halt the birds’ decline.


Caspian and fairy terns

Caspian terns

The Caspian tern or tarā nui (Hydroprogne caspia) is the largest of the terns. They are about 51 centimetres long and weigh 700 grams. They have a white body and silver-grey wings. In the breeding season their black cap tapers to a fine point above an orange-pink bill. Caspian terns feed by plunging for surface-swimming fish; they also take whitebait, bullies and eels.

These terns are found throughout the temperate world, except for South America. The New Zealand population was estimated at 1,000 breeding pairs in 1992.

The terns breed mainly around the coast, although some nest inland near Lake Rotorua and on river beds in Canterbury. Colonies are usually close to those of other terns or gulls. The birds breed from September to January and lay one to three light-flecked eggs in a shallow scrape on sand. Terns’ chief enemies are black-backed gulls, which eat the eggs and chicks. Chicks fledge at 33–38 days. Caspian terns live about 24 years.

Fairy terns

The diminutive fairy tern or tara iti (Sternula nereis) is scarcely larger than a thumb tip when newly hatched, growing to a length of just 25 centimetres and a weight of 70 grams. They have a large white frontal patch with black around the eyes, a fine-tipped yellow-orange bill, and a white body with grey wings and tail. The subspecies Sternula nereis davisae is found only in New Zealand.

They nest from November to January on sand and shell, laying one or two buff eggs with dark brown speckles. The young leave the nest at 23 days. Fairy terns feed on small fish, and can live to 11 years.

In the early 1900s fairy terns were recorded around the entire North Island coast and on South Island river beds, but by the 1980s the number of breeding pairs had dropped to four. The population in 2012 was 30–35 birds (about eight breeding pairs). In the 2000s it was New Zealand’s rarest breeding bird, and its survival remained in doubt.

Cats, rats and weasels eat fairy tern eggs, chicks and adults, and have been responsible for their decline. Storms, high tides, and people riding trail bikes and four-wheel drives also threaten the nests. The New Zealand Department of Conservation has monitored breeding and nests at Waipū, Mangawhai, and South Head, Kaipara Harbour. Their programme has included fencing off predators, relocating nests, educating the public and enforcing laws against the harming of wildlife. Even so, the 8–10 known pairs produce only a handful of fledglings most years, and in some years none at all.


White-fronted, sooty, Antarctic and Arctic terns

White-fronted terns

The white-fronted tern or tara (Sterna striata) is the most common tern living along New Zealand coasts, and on the Chatham and Auckland islands. Their name refers to the narrow white band between their black cap and bill. Their body and sharply forked tail are white, and their wings are pale grey. They are 42 centimetres long and weigh about 160 grams.

A flock of white-fronted terns diving into the sea can be a sign that kahawai fish are close by. The birds feed on small fish, such as pilchards and smelt, which the kahawai chase to the surface.

White-fronted terns bred only in New Zealand until 1979, when they also began breeding on islands in Bass Strait, between Tasmania and Australia. In autumn, large numbers of young terns and some adults fly to Australia, returning in spring for the breeding season. They nest from October to January in large colonies on beaches, shingle banks or rock stacks. They lay one or two spotted, pale green-blue to light brown eggs. The young fly at 29–35 days. They can live to 26 years.

The New Zealand population was reckoned at 12,000 to 15,000 pairs in 1997, much lower than a 1984 estimate. Detailed counts in Northland show that their numbers are dwindling. Threats include stoats, hedgehogs, rats, dogs and beach vehicles. A reduction of kahawai stocks may also be contributing to their decline.

Sooty terns

The sooty tern (Onchyoprion fuscatus) is also called the wideawake tern because of its noisy call. They nest on the Kermadec Islands, and are rarely seen on the mainland. They differ in appearance from mainland terns in that their backs are brownish black. They have a large white triangular forehead patch, and white underparts and sides of the neck. They grow to 45 centimetres long and weigh 210 grams. Their primary foods are squid, small fish and crustaceans.

Sooty terns nest in a scrape on sand and lay one cream egg between October and December. The young fledge at 30 days old. They live for up to 33 years.

With a population of around 25 million living in the world’s tropical latitudes, the sooty is the most abundant tern globally and in the New Zealand region. In 1990 it was estimated that the country was home to 22,000 breeding pairs.

Antarctic terns

The Antarctic tern is the southernmost of the New Zealand terns. The subspecies Sterna vittata bethunei breed on islands between Stewart and Macquarie islands.

These birds are 36 centimetres long and weigh 140 grams. They have a grey body and wings, a white rump and a white, sharply forked tail. During the breeding season their black cap extends down to the bill, which becomes bright red. They feed close to shore on small fish and crustaceans.

Breeding occurs between September and March. They nest in small colonies on the ground or on ledges, where they lay one or two buff-olive eggs. The young leave the nest at 27–32 days. They live to 14 years.

New Zealand has fewer than 1,000 breeding pairs. Their main predators are skuas and black-backed gulls, and on some islands feral cats also threaten eggs and chicks.

Arctic terns

The Arctic tern (Sterna paradisaea) is smaller than its Antarctic cousins, measuring 34 centimetres and weighing 110 grams. Their plumage is similar, but Arctic terns are in non-breeding plumage when Antarctic terns are breeding.

As world travellers, Arctic terns have few rivals. After breeding in the Arctic they may fly as far as 17,500 kilometres to the Antarctic before returning. Since some birds live up to 12 years, they might travel the equivalent of the distance from the earth to the moon in their lifetime. They are rare visitors to New Zealand.


Noddies

Noddies are tropical or subtropical members of the tern family. Three species are the brown, black and grey noddies. The other is the white tern. All lack the black cap of the other terns.

Only black noddies and grey ternlets live in large numbers in the New Zealand region. Their numbers are sure to increase following the eradication of rats and cats on Raoul Island in 2002.

Why are they called noddies?

Sailors may have given noddies their name because of the way the birds nod during courtship. But ‘noddy’ also means a simpleton, and the birds were thought of as stupid. Charles Darwin seemed to think so when he encountered them during his 1831–36 voyage on the Beagle: ‘The noddies, as their name expresses, are silly little creatures.’ 1

Brown noddies

The brown or common noddy (Anous stolidus) was discovered in the New Zealand region in 1989, with 25 pairs breeding on Curtis Island in the Kermadec group. Norfolk and Lord Howe islands are the other nearest breeding sites. They can also be found in the tropical and subtropical Indian, Atlantic and Pacific oceans.

Brown with a pale grey cap, they are 39 centimetres long and 200 grams in weight.

Black noddies

The black noddy (Anous tenuirostris), also known as the white-capped or lesser noddy, breeds in the Kermadec Islands, where there are about 1,100 pairs. Smaller than brown noddies, they are 34 centimetres long and weigh just 100 grams. Their plumage is dark brown, with black in front of the eye, and a silver-grey cap that extends down to a long, slender bill. They feed on fish and plankton.

Grey noddies

The grey noddy or grey ternlet (Procelsterna cerulea) is 28 centimetres long and weighs 75 grams. They are blue-grey, with a paler body that becomes progressively darker along the wings. They have a small black patch in front of the eye, and a lightly curved, slender black bill.

Grey ternlets are found in the tropical and subtropical Pacific. The New Zealand population of around 17,000 pairs breed on the Kermadecs. Some years they also breed on Three Kings and visit other islands east of the northern North Island. They lay one egg in shade on bare rock or under plants.

White terns

The white tern or white noddy (Gygis alba) breeds on Raoul Island in the Kermadec group, and on nearby Lord Howe and Norfolk islands. They are pure white, with a black eye ring, a fine-tipped, straight bill and a short, slightly forked tail. Small and slender, they grow to 31 centimetres and weigh 110 grams.

They do not build nests, but lay a single egg in the depression of a branch, in pōhutukawa or Norfolk pine trees. Hatchlings cling to the branch with their long claws. When disturbed by predators, the adults hover, flutter and make twanging and buzzing sounds.

Footnotes
    • Charles Darwin, The voyage of the Beagle, entry for 1 April, [online at http://www.online-literature.com/darwin/voyage_beagle/20/] › Back

Skuas

Skuas are aggressive seabirds that rob other birds of their food, prey on eggs, chicks (such as fatty muttonbirds) and fish, and scavenge for sheep, cattle, seal and sea lion carcasses. Although skuas are occasionally found around mainland coasts, they are more often seen on the Chatham and subantarctic islands, and in Antarctica. Of the five species recorded in the New Zealand region, subantarctic skuas are the only ones that breed there. The skuas most commonly seen on New Zealand coasts are Arctic skuas – visitors from the northern hemisphere.

Subantarctic skuas

Known to Māori as hākoakoa, the subantarctic, southern or brown skua (Catharacta antarctica lonnbergi) breeds in New Zealand, throughout the Southern Ocean, and on islands of the Indian, Atlantic and Pacific oceans down to Antarctica.

Relatively large and stocky, skuas are dark brown with white flashes on the wings. They have a sturdy, hooked bill. Adults grow to 63 centimetres long, with males weighing 1.76 kilograms and females 1.95 kilograms.

Subantarctic skuas breed on islands off Stewart Island and the Chatham, Snares, Antipodes, Auckland and Campbell islands. 

Skua females lay two eggs from September to December, and the young are fed for 4–5 months. Unlike any other seabirds, 10% of subantarctic skuas on the Chatham, Snares and Stewart islands tend their nests in cooperative groups, usually consisting of a female and two or more unrelated males. Some trios remain together for many years.

The New Zealand population is fewer than 2,000, and subantarctic skuas are partially protected (they may be killed as pests by landowners). Scientists believe that numbers are dwindling, although there has been no systematic monitoring. The reduction has been linked to plummeting numbers of penguins and elephant seals – the carcasses of which are favourite food for skuas – on subantarctic islands. Another problem is farmers and fishers shooting them.

South Polar skuas

The South Polar skua (Catharacta maccormicki) breeds on the Antarctic continent and its offshore islands. They spend winter at sea, including offshore New Zealand, and some head to the northern hemisphere. They feed on shoaling fish, and take eggs, chicks and spilt krill from penguin and petrel colonies.

These skuas are 59 centimetres long, with males weighing 1.27 kilograms and females 1.42 kilograms. The New Zealand-administered Ross Dependency has an estimated population of 15,000 South Polar skuas.

Skewered

Why do skua chicks kill their siblings? Evolutionary biologists who have puzzled over this have considered that parents produce more offspring than they can raise, resulting in a fight to the death over resources. To test this, two New Zealand scientists gave supplementary food to South Polar skua parents. Still, the chicks killed their siblings. The explanation was that skuas are naturally aggressive.

Arctic skuas

The Arctic skua (Stercorarius parasiticus) breeds in the Arctic and spends the northern winter in southern hemisphere seas. Common visitors to New Zealand coastal and inshore waters from November to April, they are more likely to be seen than the New Zealand-breeding subantarctic skuas. They feed by stealing the catch of terns and gulls in mid-air. They are relatively small, at 43 centimetres long and 400 grams in weight.


Hononga, rauemi nō waho

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How to cite this page: Gerard Hutching, 'Gulls, terns and skuas', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/mi/gulls-terns-and-skuas/print (accessed 26 August 2019)

Story by Gerard Hutching, published 12 Jun 2006, reviewed & revised 17 Feb 2015