Story: Wetland birds
Page 3 – Bitterns and spoonbills
Australasian bittern – matuku
The Australasian bittern or matuku (Botaurus poiciloptilus) is a heron-like bird that lives in shallow, densely vegetated wetlands. It hides among raupō (bulrush), reeds and scrub by standing stock-still with its bill vertical, even swaying with the surrounding plants on a windy day.
The bittern is mottled brown with long legs and neck. Stockier than a heron, it is about 70 centimetres long; males weigh 1.4 kilograms, females 1 kilogram.
Bitterns hunt fish, frogs, eels, mice and young birds.
The male’s foghorn-like boom in the evenings during the breeding season (June to February) is the best sign of the bittern’s presence. He booms to attract females, and to guard the territory from other males.
Rear guard action
Māori believed that the bittern made a booming noise from its backside, with its sharp bill stuck into the ground. The Ngāti Awa historian and tohunga (priest) Hāmiora Pio suggested that these blasts were caused by the bird struggling to overcome a writhing eel.
While the male defends the territory, the female bittern makes the nest, breaking down reeds to form a platform 25–30 centimetres above the water. She incubates the eggs and feeds the hatchlings.
A census in 1980 found just 600–700 birds, thinly scattered over the North and South islands. Their numbers have fallen due to drainage of wetlands, and they are nationally endangered.
Australasian bitterns are native to New Zealand, southern Australia, New Caledonia and the Loyalty Islands.
Royal spoonbill – kōtuku-ngutupapa
The royal spoonbill (Platalea regia) has a long flat bill with a spoon-shaped tip. In the same family as ibises, it is a stork-like bird with long legs and neck. The royal spoonbill or kōtuku-ngutupapa is a self-introduced native; yellow-billed spoonbills also occasionally visit New Zealand.
The royal spoonbill is brilliant white with a black bill, face and legs. It measures about 77 centimetres from bill tip to tail, and weighs 1.7 kilograms. During breeding, pale-yellow breast feathers form, and long plumes behind the head are raised during courtship displays.
To feed, spoonbills stand knee-deep in water, sweeping their bill from side to side in wide arcs. This creates swirls, drawing in small invertebrates, fish or frogs from the surrounding water or muddy bottom. Spoonbills sense their prey by touch, feeding by day or night whenever the tide is right.
Establishment in New Zealand
In the past, royal spoonbills occasionally reached New Zealand in winter. The first recorded breeding was at the kōtuku (white heron) colony in South Westland in 1949. Numbers have fluctuated, but a 2000 winter census counted 956 – so they are well established.
Breeding and dispersal
Royal spoonbills breed at about eight coastal sites, some of them near kōtuku, shag and gull colonies. Some nests are high in kahikatea trees, others on low shrubs or on the ground. After breeding they disperse to estuaries and wetlands around the country. Small flocks fly in a V formation.