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Herons

by  Gerard Hutching

Most celebrated of New Zealand’s herons are rare white herons, or kōtuku, but there are several other species in this group of elegant birds.


White herons – kōtuku

A rare bird

Rare in New Zealand, with a population of just 100–120 birds, the elegant white heron or kōtuku (Ardea modesta) is nevertheless common in India, Japan, China and Australia, where it is known as the great egret. With a long, slender neck, yellow bill and thin legs, white herons grow to 92 centimetres in length and 900 grams in weight. In flight their long neck is held kinked. During breeding their bill darkens and a veil of fine feathers extends beyond the folded wings and tail, accentuating their graceful profile.

Kōtuku had mythical status for Māori because of their rarity and beauty. The epithet ‘te kōtuku rerenga tahi’ (the white heron of a single flight) was given to distinguished guests who seldom visited.

Australian immigrants

It is not known exactly when the only heronry in New Zealand – near Ōkārito in south Westland – became established, but it is presumed that a few hundred years ago a favourable wind carried some birds over from Australia. This sometimes still occurs: in the winter of 2013 many trans-Tasman strays appeared throughout the country, forming small flocks of five to seven birds from Otago north to Hawke's Bay.

The Waitangiroto colony

White herons have not spread out to form new breeding colonies elsewhere, although they disperse widely during winter before returning to Waitangiroto (near Ōkārito) to nest. Some birds scatter to northern estuaries; others may occasionally harass goldfish in city gardens, or be driven by winds as far as the Chathams or subantarctic islands (although these birds may come direct from Australia). Otherwise they feed mainly in estuaries on a diet of whitebait, small fish and eels, aquatic insects, shrimps, tadpoles and frogs.

Māori had probably long known about the colony, set in dense forest alongside the sluggish Waitangiroto River. They captured individual kōtuku, but ensured that the total population remained viable. Birds were kept in cages and every few months one of the feathers was plucked for use as an adornment.

Important plumage

The long breeding feathers of kōtuku were considered by Māori to be tapu, and were used to adorn the hair of chiefs and other men of high rank, or their cloaks and kites. Women wore only the shorter plumes. If a man dreamt that he saw the skull of his ancestors decorated with kōtuku feathers, it meant his wife’s baby would be a boy; the black feathers of the huia foretold the birth of a girl.

When European settlers discovered the colony in 1865, vandals destroyed the nests and eggs, and the feathers were taken for fashionable women to wear in their hats. By 1940 there were only four nests left.

Protection

First steps to protect the area were taken in 1924, when a 60-metre-wide strip on either side of the Waitangiroto River was declared a sanctuary from logging. In 1941 it was declared a fauna and flora reserve. It was guarded by a resident warden, and access to the ground was controlled during the breeding season. In 1957 the colony was gazetted as a wildlife refuge, and it became the Waitangiroto Nature Reserve in 1976.

Surrounded by swamps and rivers, the colony has some natural protection, although not enough to prevent stoats and harrier hawks preying on chicks and fledglings. To help these young survive, the New Zealand Department of Conservation runs a stoat-trapping programme.

Limited numbers of tourists can visit the colony during the breeding season. The birds are viewed from a hide across the river to avoid disturbing them.

Settled existence

The Waitangiroto colony is unusually long lasting, with only minor movement within the same general area. In the United States the average lifespan of a heron colony is only five years, and in Australia 18 years. There are two main reasons for the colony’s longevity: the number of birds is relatively small, so vegetation is not killed off, and visitors are kept to a minimum and concealed in a hide, so they do not frighten the herons away.

Breeding

In August and September white herons arrive at the Waitangiroto colony to nest in kāmahi, māhoe and kōwhai trees, and in the crowns of tree ferns. The birds undergo a transformation: their bills turn black and they develop long, white, loose breeding plumes on their backs and wings. Females lay three to five pale blue-green eggs in September or October, and both sexes share incubation. When the chicks hatch, they are fed by both parents until they fledge at around 42 days. They disperse from the colony three weeks later and may live up to 22 years.

Since observation began in 1944, the number of recorded nests reached a high of 65, with 60 fledglings, in 1981. Since 1982 the number of nests has remained at around 40–50.

Climate is key to the survival of chicks. Since 1950 the westerly airflow to New Zealand has increased, causing more storms and greater rainfall in Westland, especially in summer. These have destroyed nests and killed chicks in some years. The Ōkārito Lagoon occasionally floods, preventing adult white herons from fishing for their staples of whitebait, eels or freshwater crayfish, which means they cannot feed their young. This has happened with increased frequency since 1967.


Other herons

Three of the four heron species that breed in New Zealand – the white heron, white-faced heron and nankeen night heron – are at home in a variety of habitats, including estuaries, sandy or rocky shores, mudflats, wetlands, and river and lake margins. The reef heron is a coastal bird and is never seen inland. All four species have long legs and necks, and spear-like bills which they use to catch fish in shallow water. They are often solitary birds, but white-faced herons and white herons sometimes form small flocks, and nankeen night herons roost communally.

Reef herons

The dark-grey reef heron or matuku moana (Egretta sacra) is 66 centimetres long and weighs 400 grams. Their yellow-orange eyes and bill are striking, and during breeding they have long filamentous feathers on their head and back.

Reef herons can be found in Australia, Japan and eastern Asia, and they are distributed throughout the Pacific, where a white form of the species is common. Exclusively a coastal bird, its strongholds in New Zealand are Northland, the Coromandel Peninsula and the Marlborough Sounds.

These birds eat small fish and small eels, crabs and molluscs, which they sometimes catch with a clever ploy: they spread their wings around in front and snap up the fish, which are attracted to the temporary shadow.

Reef herons nest in crevices or beneath overhangs or vegetation. In September to December they lay two to four pale blue-green eggs, which both parents incubate. The young fledge at about six weeks, and live up to 14 years.

White-faced herons

An Australian immigrant which began breeding in New Zealand only in the 1940s, the white-faced heron (Egretta novaehollandiae) has become the most populous heron in the country. Adaptable birds, they are equally at home along the coast or inland. They feed in aquatic environments and damp pastures, taking fish, tadpoles, frogs, insects, spiders, worms and even mice. They are about 66 centimetres long and weigh 550 grams.

Like other herons, male and female white-faced herons share in the raising of their young. They build the nest together, usually high in trees, and take turns to incubate the eggs and feed the nestlings. Breeding takes place any time between June and October, and from the three to five pale blue-green eggs, usually only two young survive. The chicks are wary of leaving the nest before they can fly – in contrast to nestlings of other herons, which like to clamber around the nesting tree until the parent returns with food. White-faced heron fledglings leave the nest at six weeks.

Nankeen night herons

Nankeen or rufous night herons (Nycticorax caledonicus) turned up on the Whanganui River between Pipiriki and Jerusalem in the early 1990s and started breeding. The population there was estimated at 50 birds in 2012. They are reddish-brown with a black cap, and have a short neck. Although their name suggests they are nocturnal, these herons sometimes feed during the day when breeding. Their main foods are fish, aquatic insects and frogs. Small and heavy compared to other New Zealand herons, nankeen night herons are 57 centimetres long and weigh 800 grams, and they fly with heavy wingbeats. They lay two to five pale blue-green eggs in September or October, and live up to 21 years. The young leave the nest within 50 days of hatching. They look very different from adults, being brown streaked with buff all over.

Seasonal visitors: cattle egret and little egret

Two species of herons – the cattle egret (Ardea ibis) and little egret (Egretta garzetta) – fly from Australia in May to spend winter on New Zealand farmland or coasts before returning to Australia in September to breed. A third of the size of white herons, these birds are sometimes mistaken for them.

Cattle egrets are much more common in New Zealand than little egrets, and are usually seen in flocks among cattle. Yellow-orange breeding plumage begins to show on their head and breast around September.


Hononga, rauemi nō waho

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How to cite this page: Gerard Hutching, 'Herons', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/mi/herons/print (accessed 7 June 2020)

He kōrero nā Gerard Hutching, i tāngia i te 12 Jun 2006, reviewed & revised 17 Feb 2015