New Zealand’s smallest bird is the rifleman or tītiti pounamu (Acanthisitta chloris). It belongs to an ancient endemic family of Gondwanan origin, Acanthisittidae (New Zealand wrens) in the Passeriformes (perching birds) order. This family of just two surviving species – the rifleman and rock wren – is a separate group from all other 5,000 birds in that order.
Wearing of the green
The rifleman’s English, Māori and scientific names all refer to the male’s green plumage: New Zealand Infantry riflemen wore green coats, pounamu is the Māori word for greenstone, and chloris is Greek for yellowish green.
The male’s back plumage is green, and the female’s is flecked brown. Just 8 centimetres long, they have no tail to speak of, and their tiny body is almost round. The male weighs 6 grams, the female 7 grams – one-third of the weight of a house mouse. The rifleman’s delicate thorn-like bill is slightly upturned, and its fine black legs end in oversized toes (three pointing forward and one back, like other passerines).
Riflemen move around the forest in short aerial hops, clinging easily to rough tree trunks. Working their way up a tree, they take spiders, beetles, small wētā, caterpillars and moths from foliage and cracks in the bark. Adults and young often forage close together. They keep in contact with a high-pitched buzzing call, a single note that is out of hearing range for some people. Each pair has its own territory, which both males and females defend.
The rifleman and the alpine rock wren are the only remaining species of the ancient New Zealand wren family. Five other species – four of them flightless – were made extinct by introduced predators. Feral cats had wiped out the last Stephens Island wren by 1894. The most recent loss was the bush wren. Once widespread, its gradual disappearance went almost unnoticed. It was last seen around 1972.
Breeding and life span
The male builds nests in tree or rock hollows, helped by the female. Over a week, she lays four white eggs, each weighing 1.5 grams – almost one-quarter of her weight. The male tops up the female’s food intake to help with the huge nutritional demands of egg production.
Riflemen can live for six years, but 1½ to three years is more usual.
Habitat and distribution
Riflemen live in a variety of forest types: lowland conifer–broadleaf forest, high-altitude beech forest, mature tawa forest and mānuka–kānuka scrub.
They were once common throughout New Zealand, but farmland, towns and highways have fragmented their forest habitat. Riflemen don’t fly over open treeless ground, so once they disappear from an area they cannot return. In the North Island, they are found south of the Coromandel Peninsula (apart from Little Barrier Island and a tiny isolated group in Northland). Their distribution is patchy. In the South Island they still live in many forest areas of the main ranges, in bush patches on Banks Peninsula, Otago Peninsula and the Catlins. Their numbers have increased considerably where predators have been controlled. Riflemen have been relocated to Tiritiri Matangi and Ulva islands.