Story: Large forest birds
Page 2 – Weka
The weka (Gallirallus australis), a flightless rail, has an engaging and resourceful nature. Weka are most often seen or heard shrieking around dusk. They emerge from dense undergrowth and scurry, neck outstretched, across open space to the next available cover. Weka live mainly at forest margins, and make forays onto farmland and gardens, where they helpfully eat grubs and unhelpfully pull up seedlings.
There are four subspecies:
- the North Island weka
- the western weka (found in north-west Nelson, Marlborough and the West Coast)
- the Stewart Island weka
- the buff weka (extinct in the eastern South Island, but introduced to the Chatham Islands).
The buff weka became extinct in its eastern South Island range around 1920, but was introduced to the Chatham Islands. Several attempts have been made to re-establish populations in Canterbury and Otago.
Weka are protected throughout their natural range – the North, South and Stewart islands – but may be hunted on the Chatham Islands and some tītī (muttonbird) islands off Stewart Island.
On the Chatham Islands, 800 kilometres east of New Zealand, weka are part of life. Hunting and feasting on them is a social pastime. Just as mainland New Zealanders are often called Kiwis, the nickname for a Chatham Islander is Weka.
Weka are large brown rails, about 50 centimetres long, with a strong tapered bill, sturdy legs and reduced wings. Depending on the subspecies, male weka weigh around 1 kilogram and females 700 grams. All have brown plumage streaked with black, but the shade varies from the pale-brown buff weka to the western subspecies, some of which are almost black.
Weka are sometimes confused with the smaller banded rail. Unlike the weka, this bird has black and white horizontal bars on the underside, and can fly.
Weka are omnivorous – animal foods form 30% of their diet, and plant foods make up the rest. Animal foods include earthworms, larvae, beetles, wētā, ants, grass grubs, slugs, snails, insect eggs, slaters, frogs, spiders, rats, mice, and small birds and eggs. Plant foods include leaves, grass, berries and seeds. Weka are important in the bush as seed dispersers. They distribute seeds too large to be spread by smaller berry-eating birds.
For a flightless bird, the weka can travel remarkable distances. Conservation workers report that it took one weka just three weeks to walk from its release site, the Waitākere Range near Auckland, to Tāneatua, 300 kilometres away. It was heading for its home near Gisborne.
Female weka lay three creamy or pinkish eggs on average. After a month the chicks hatch, and are fed by both parents until they are fully grown at between six and ten weeks. The breeding season varies, but when food is plentiful, weka can breed year round, raising up to four broods.
Weka and humans
The meat, skin, oil and feathers of weka were important resources for Māori, and for European explorers, who called the birds bush hens or woodhens. Weka are easily tamed with food, and forest campers learn not to leave food or shiny objects lying within reach of these inquisitive, acquisitive birds.
Introduced to islands
Weka have been introduced to many islands, where they have done well in the absence of other predators. However, they have sometimes become a pest to other endangered species, as they eat small birds, lizards and insects. In the 1870s they were introduced to Australia’s subantarctic Macquarie Island as food for sealers, and helped drive the Macquarie Island parakeet and a land rail to extinction. Weka were eradicated from the island in 1988.
In 1905, 12 buff weka were introduced to the Chatham Islands. Their descendants now number around 60,000, and islanders are allowed to harvest them, with an estimated 5,000 birds taken each year. Weka may also be killed on the Tītī Islands around Stewart Island.
Weka as pests
Because they prey on endangered species, weka have been removed from important conservation islands. In the 1980s, thousands were moved from Codfish Island to neighbouring Stewart Island to protect endangered Cook’s petrels and South Georgian diving petrels, and to prepare Codfish Island for the release of kākāpō.
Weka have been regularly removed from Maud Island in the Marlborough Sounds, a predator-free sanctuary. But the birds aren’t easily deterred. In 1978, three weka were given numbered bands before being released several kilometres away on the mainland. The trio were back on the island within days, after a long trudge and a 900-metre swim against a 4-knot current.
Threats to weka
Despite their feisty nature, weka are in decline through most of their natural range. Dogs, ferrets, stoats and cats kill them, and disease and drought are also a factor. The main remaining North Island population, in the Raukūmara Range, was estimated at 2,000 birds in 2005.
In the 1990s conservationists started a breeding programme for the North Island weka. They released birds on the Russell Peninsula in Northland, and on Pakatoa Island (Hauraki Gulf) and Whanganui Island (Coromandel) – islands without other endangered species that the weka could harm. The island populations have thrived. Islands on Otago lakes are also home to buff weka, relocated from Chatham Island.