South Island Kōkako

South Island Kōkako

T here are species in New Zealand of so ancient a lineage that it is certain that they have been in this country since before the time when New Zealand first became an oceanic island or archipelago.

One of these species is the Kokako, belonging, with the extinct Huia and Tieke, the saddleback, to the ancient wattlebird family, Callaeidae. The common ancestor of these birds probably became isolated when the super continent, Gondwanaland, began to fragment some 80 million years ago. These birds are found nowhere else in the world, nor do they have any obvious living relatives.

Historically, the range of the Kokako has shrunk as its forest home has shrunk. Three quarters of the native forests present 1000 years ago before the arrival of humans have now gone. The mammalian predators that overrun the remaining forests and threaten Kokako today are quite different to the bird predators that hunted their ancestors a thousand years ago.

The dawn chorus of the Kokako was a common sound in the forest before European settlement. Indeed it was said to be far more numerous than the Tui but today one has to travel to one of the few areas remaining to the Kokako, such as the Mainland Island Restoration Project at Otamatuna in Te Urewera National Park, to hear its haunting song.

As the sunlight moves up across the bush to touch the tallest trees, the Kokako appears high in one of the trees on a ridge. It begins its morning performance by opening and closing its wings and fanning its tail. It then arches its neck and utters some gentle mewing and buzzing sounds before calling out across the valley. The incredibly beautiful melodious organ–like notes hang over the valley before being answered by another of its kind, somehow enhanced and made more poignant by the dark brooding quality of the bush. Male and female may sing together for periods of up to half an hour, performing a duet of impressive harmony and complexity. Neighbouring Kokako may join in singing the same themes, resulting in a rondo-like chorus.

The bird itself is as lovely as its voice. Predominantly blue–grey, the bill and legs are black along with a distinctive velvet black mask. The North Island species has ultramarine wattles under the throat. The South Island bird has orange wattles but this bird is now believed to be extinct.

It is only possible to distinguish the sexes after careful study of their behaviour as both sexes are very similar in size, colour and form. Like other wattlebirds, the Kokako flies poorly on short rounded wings. It prefers to use its powerful legs for leaping, running and jumping through the trees.

They eat a wide range of food, fruits, leaves and insects. They defend 5–20 hectare territories in which they obtain all their resources. Singing is used to maintain their territories. They sing mostly at dawn and always from the top of tall trees on ridges in the higher parts of their territory. In addition to song, Kokako communicate with a variety of calls, clicks, buzzes, cat–like noises and screeches, all used in particular social contexts. Pairs remain together all year and apparently for life, never being separated by much more than the distance of a quiet call.

Kokako reproduce slowly, a characteristic exhibited by many of New Zealand’s endemic birds. The immediate cause of Kokako decline is recruitment failure, the loss of offspring, due to predation by ship rats and possums at Kokako nests. In addition, many females are killed by predators while nesting. However, these declines can be reversed by intensive and sustained pest control.

According to a recently published document, less than 400 pairs of Kokako currently exist. Populations are small and isolated and most are male. The largest population by far is in the tawa dominated northern forests of Te Urewera National Park. The only other mainland island populations with more than 20 females are at Mapara and Pureora in the King Country and Kaharoa and Rotoehu in the Bay of Plenty.

The main objective of the Kokako Recovery Plan is to restore the species to most of its former range through Mainland Island projects throughout the country. It is an ambitious project and one that depends heavily on the ongoing generosity of the tax paying public. The war against predators must be sustained otherwise the monies already spent would be wasted.

Narena Olliver — Waiotahi Valley, Opotiki, 1998.