Back from the Brink

Forest and Bird, Issue 294, 1 November 1999, Page 28

Back from the Brink

HUGH ROBERTSON

> te Pi AM ‘New Zealand scientists have helped. rescue : ‘the Rarotengan flycatcher from: ‘extinction, |

writes

nce among the 10 rarest birds in world, the Rarotongan flycatcher or kakerori has been brought back from the brink of extinction. When rescue work began in 1989 there were only 29 birds left and extinction was predicted by 1998. However, thanks to one of the most successful bird-conservation programmes ever undertaken, numbers have instead rebounded and the kakerori is no longer regarded as ‘critically endangered. The special feature of the recovery programme, led by New Zealand scientists, is that all the management has taken place within the natural habitat of the species. The kakerori Pomarea dimidiata, is a small forest bird found only on the island of Rarotonga in the Cook Islands. Distantly related to the fantail in New Zealand, it more closely resembles a whitehead or yellowhead in its shape, size and feeding behaviour. For the first two years of life, kakerori are bright orange, then in their third year they become mottled-orange and grey, and from the fourth year onwards they have a dark-grey back and paler-grey underparts. They are one of the Pomarea flycatchers found throughout eastern Polynesia, and all five species are threatened with extinction. In 1989, the kakerori and the Tahiti flycatcher were among the 10 rarest bird species in the world. Missionaries wrote that kakerori were abundant on Rarotonga until at least the mid-1800s; but the arrival of ship rats spelt doom for them in the same way as they did for many forest birds in New Zealand. Like our species, these birds of oceanic islands evolved in the absence of mammalian predators. While they coped with invasions by the relatively benign Pacific rat or kiore, the introduction of ship rats was too much. A few birds were collected for museums around the turn of the century but, for most of the 1900s, it was thought that the kakerori had gone the way of no return, like the huia, piopio and bush wren in New Zealand. Then, in 1973, a small pocket of birds was re-discovered in the rugged foothills of Rarotonga. In 1984, New Zealand scientists Rod Hay and Gerald McCormack made a rapid census. They found 24 birds, and

colour-banded eight of them (see Forest & Bird, August 1984). A thorough census by Rod Hay and myself in September 1987 revealed 38 birds, including five of the colour-banded birds. Observations over the next two breeding seasons showed that an alarming 80 percent of nests failed to produce young. This was mainly because of predation by ship rats, though at least one adult kakerori was killed by a feral cat. By 1989, there were 29 birds left, including just 13 females — mathematical modelling predicted there was a 50 percent chance they would be extinct by 1998 unless something was done urgently. Ed Saul joined the rescue team in 1989 and, working closely with the fledgling Cook Islands Conservation Service, we started a ‘research-by-management programme. We began experimentally poisoning rats over an increasingly large part of the 155hectare range of the birds. Poison bait stations (in 40cm sections of Novacoil drainpipe) were laid out along ridges surrounding the valleys occupied by kakerori, and on twisting tracks mainly following the contours within the valleys, where most nests are found. Since then a variety of poison baits has been used, but the preferred choice is Talon 50WB (waxy block) baits, because rats like them and they persist reasonably well in the hot humid environment. From late September to December baits are replenished or replaced weekly by a small team of (increasingly fit!) conservation workers and volunteers led by Ed Saul. The aim is to knock down rat numbers by the time the first kakerori nests appear in mid-October, and then maintain low num-

bers of rats through until December when the breeding season is starting to tail off. Feral cats are incidentally killed by eating poisoned rats, or sometimes by eating baits hooked out from the bait stations. Wherever possible, nests are given extra protection from rats by nailing a band of aluminium around the trunk of the nest tree and any nearby trees with interlacing branches. The intitial success of the rat poisoning programme is assessed by recording the decline of bait-take as the weeks pass and by the amount of nesting success. The ultimate test is the the number of yearlings alive and the total population size during the annual census in the following August. This roll-call of birds is possible because about two-thirds of the birds have now been mist-netted and marked with a unique combination of coloured plastic leg-bands. The unbanded birds are either highly faithful to their territories or can be distinguished by their particular plumage type. The population of kakerori has grown from the 29 birds of 1989 to a minimum of 180 birds in 1999. This growth has been made possible by a combination of nesting success (increasing from 20 percent to 67 percent), and the increasing rate of survival of the adult birds (up from 76 percent to an amazing 93 percent). This gives a mean lifeexpectancy now of 13 years.

Kakerori are among the longest-lived wild birds for their size. Three of the eight birds colour-banded as adults in 1984 were still alive in August 1999 at a minimum age of 18 years, 10 months. Five others are known to be at least 16 years old. Almost unbelievably, 18 of the 29 birds alive in 1989 were still alive a decade later. In this way, kakerori have a similar life history to many long-lived New Zealand birds such as kiwi, kakapo and kokako. Their life expectancy is quite different from the short-lived perching birds of the Northern Hemisphere which are lucky to live much more than five years. y" ince 1996, the management of the "Mp Kakerori Recovery Programme has ma passed from the Environment Service (formerly the Cook Islands Conservation Service) to the three families who own the forest occupied by the kakerori. Known as the Takitumu Conservation Area the project is part of the South Pacific Biodiversity Conservation Programme run by the South Pacific Regional Environment Programme. Under this programme, customary landowners conserve the biodiversity in a defined area and at the same time develop a sustainable economic use of the area. In this case sustainable use is through ecotourism. Anna Tiraa, a stalwart of the rat-poisoning campaigns and nest monitoring, was instrumental in getting this project off the ground; Ed Saul has remained the backbone of the recovery programme and has been the principal technical adviser to the project. The 155 hectares of Takitumu host all five species of native land-bird found on Rarotonga. Here, too, are found most of the sea-birds (tropicbirds, terns and noddies) of Rarotonga. There are numerous

lizards (which have benefited greatly from the rat- and cat-control programme), a large colony of fruit bats (flying fox or moakirikiri), and a wide variety of native plants. These plants include several rare and unusual orchids and mistletoes. Tracks have been constructed through one of the four valleys occupied by kakerori to allow tourists of varying levels of fitness to be catered for, and an interpretation centre is close to completion. During the kakerori breeding season some side valleys are closed off, but visitors are permitted to see certain kakerori nests from a distance. Year round, all visitors are assured of seeing and hearing kakerori (and lots more) during their half-day guided tour for $35 per person — contact the Takitumu Conservation Area Project at PO Box 3036, Rarotonga; phone (00682)

29906, or email: kakerori@tca.co.ck The Kakerori Recovery Programme has been extremely successful and is now promoted as a model for other conservation work in the region. In this particular case, the threat was straightforward — just two species of introduced predator, the ship rat and feral cat. The answer to the problems they posed was also simple — poisoning ship rats also led to secondary poisoning of feral cats. These two predators are also the main threats to many other endangered birds in the South Pacific. The technologies developed in New Zealand, and during the Kakerori Recovery Programme, are now being used elsewhere in the region to try to conserve other birds, especially the critically endangered cousin of the kakerori, the Tahiti flycatcher Pomarea nigra.

Ithough the kakerori population A: Rarotonga has recovered spectacularly, it remains at risk from threats such as cyclones, new bird diseases, and new predators (such as snakes) that could accidentally get to Rarotonga. An overnight storm in late July 1998 apparently killed about half of the yearlings from the preceding season, and provides a warn-

ing about the potential impact of a severe cyclone. Conservation efforts are now being directed toward determining the feasibility of shifting some kakerori to another island, in the southern Cook Islands, which is free of ship rats: this is simply an insurance policy, so that Rarotonga can be re-stocked if disaster strikes there. Meanwhile, through this programme, the kakerori has gone from an obscure forest bird unknown to most Rarotongans, to an emblem of the island which many Rarotongans are proud of. A local rugby team has even adopted the name Kakerori — surely the ultimate measure of advocacy success! Further, the establishment of a successful eco-tourism business by the land-owning families also shows that conservation and economic development can work hand in hand. HUGH ROBERTSON is a scientist with the Department of Conservation in Wellington where he is head of the Kiwi Recovery Programme. Some 10 percent of his time is devoted to giving scientific advice to the Kakerori Recovery Programme, with travel costs paid by the Ornithological Society of New Zealand, the Pacific Development and Conservation Trust, and the South Pacific Regional Environment Programme.