Story: Large forest birds
Page 7 – Kōkako
Hauntingly beautiful songsters, the North Island kōkako (Callaeas wilsoni) and South Island kōkako (C. cinerea) are wattlebirds.
The other New Zealand wattlebirds are the rare saddleback (Philesturnus carunculatus) and the extinct huia (Heteralocha acutirostris). Together they form the endemic Callaeatidae family. Not related to the Australian wattled honeyeaters, they are among New Zealand’s most ancient flying birds. Their ancestors may have been on the land mass that split from the supercontinent of Gondwana to become New Zealand.
Kōkako weigh around 230 grams and are 38 centimetres long. They have long legs and a long tail, and a short, strong bill. The North Island kōkako has distinctive blue wattles (fleshy pads hanging from each corner of the bill), while the South Island bird’s wattles were orange. Named the blue-wattled crow and orange-wattled crow by early Europeans, both have striking blue-grey plumage and a black face mask.
The grey ghost
The South Island kōkako was seen up to the 1960s, and is now officially presumed extinct. But occasional reports of its call or other signs give tantalising hope of finding a remnant population of this blue-grey bird.
Of all New Zealand forest birds, the kōkako is considered to have the most beautiful song. Bushmen called it the ‘true bellbird’ or ‘organ-bird’. In 1870, ornithologist Walter Buller wrote:
I have often heard two or more Kokakos, each in a different key, sounding forth these rich organ-notes with rapturous effect; and it is well worth a night’s discomfort in the bush to be awakened at dawn by this rare forest music. 1
Its other calls sound like a cackle, a mewing cat, and the soft tolling of a distant bell.
Kōkako song varies from region to region, and the birds respond less to kōkako from outside their home patch. South Island kōkako only called around breeding time, which has added to the difficulty of locating them.
Territory and habitat
Single kōkako as well as pairs establish year-round territories of 4 to 12 hectares, where they feed and breed. They sing to maintain their boundaries and to attract a mate. Their short, rounded wings allow flights and glides of up to 50 metres. Otherwise they move along tree branches from one level up to another, running and hopping on their long legs. They prefer diverse lowland forest, which has a range of storeys and enough variety for year-round food.
Kōkako have a mixed diet which varies with the seasons. Leaves, fern fronds and some insects keep them going through the winter, and once spring arrives, nectar and leaf buds are more plentiful. Over summer they mainly eat moths, caterpillars, wētā and other invertebrates, as well as fruit.
When food is abundant, kōkako raise more than one brood of chicks a year. Nesting can take place from October to March. The female lays two or three pinkish-grey eggs, which she incubates alone for 20 days. The male feeds her on or near the nest, and later both feed the chicks, which fledge in 30 to 45 days. Young remain partially dependent for food from four months to a year.
Kōkako under threat
Kōkako were once abundant, but today North Island kōkako remain in just a handful of places – mainly in the northern Urewera, Bay of Plenty, and the King Country. A few also survive in Northland’s kauri forests.
The species is now endangered. In the late 1980s, it was estimated that 350 pairs remained. Thanks to conservation efforts, by 2006 there were around 1,400 birds, including 640 breeding pairs.
Kōkako need large unbroken areas of diverse forest, so the loss or fragmentation of forest is one reason for their decline. Today their remaining forests are largely protected. But rats, possums and stoats raid kōkako nests for eggs and chicks. One study found that for every 10 breeding pairs, just one chick a year survived – not nearly enough to maintain the population.
Conservation efforts focus on improving the breeding success of kōkako.
In Māori tradition the kōkako carried water in its wattles to the demigod Māui, to help him in his battle against the sun. Māui rewarded the bird by making its legs long and slender so it could move easily through the forest.
Some kōkako populations have done well in ‘mainland islands’ – conservation areas on the mainland, intensively managed to reduce predators and restore vegetation. Kōkako have also recently been reintroduced to two forests where they existed up until the mid-1900s. To preserve genetic diversity, birds from tiny remnant populations are rescued for breeding programmes.
Kōkako transferred to Hauturu (Little Barrier Island) from the 1980s show how well they can do with fewer predators. The 34 birds increased to 200 pairs by 2005. Recent transfers to predator-free Kapiti and Tiritiri Matangi islands are also proving successful.