The Waning of Weka

Forest and Bird, Issue 297, 1 August 2000, Page 18

The Waning of Weka

and

ANN

BASIL GRAEME

A Forest and Bird dream to save the North Island weka becomes a nightmare.

report on the experience.

e had a dream. We dreamt that we could bring the vanishing weka back to its old haunts in the North Island. Our dream has yet to come true — and it might never do that — but over the 10 years of Forest and Bird’s weka project we gained some ground for the beleaguered North Island weka, had many adventures, and found an intrepid group of weka enthusiasts, among our members, land owners, and DoC field officers. We began at the end of the 1980s when there was considerable optimism abroad

amongst conservationists. We had a recently formed Department of Conservation looking after most of our publicly owned native forests, and we had forged an Accord with the forestry companies that promised to reduce the destruction of privately owned native forests. The tide of habitat loss seemed to be turning, yet native birds were still dwindling. So we decided to try to help a species not yet in trouble — building a fence at the top of the cliff instead of parking an ambulance at the bottom. We chose the North Island weka. Its widespread disappearance early this century was attributed to many

causes, including introduced diseases. But it is a robust bird and was still apparently thriving around East Cape and Gisborne despite droughts, hunting, predators, clearance of bracken and scrub, and loss of roadside vegetation. Perhaps the disease that had decimated the early weka populations had passed. And although we knew transported weka populations had failed to take root in the past, we hoped we could do better. Perhaps we could breed and release weka to found new populations elsewhere in the North Island. Perhaps we could help the cheeky weka to become widespread and common again.

As soon as the project began, it encountered omens. DoC instructed us to survey a known stronghold of weka, yet we found scarcely any birds. The more we and the Department looked for weka, the fewer we found. Weka numbers in the East Coast had crashed. Perhaps the trouble was triggered by starvation in the severe drought of 1982-83, which was followed by the disastrous flooding of Cyclone Bola. From more than 88,000 birds in the early 1980s, East Coast weka numbered fewer than 5000 in 1991. That year, the North Island weka had to be declared a threatened species. Already our ‘fence at the top of the cliff? was becoming an ‘ambulance at the bottom’. With the altered status of weka, we could not take birds willy nilly from the wild. Instead we began our breeding programme with young birds caught on the Mansion House lawn on Kawau Island, paired with captive-bred birds from Otorohanga Kiwi House. In 1991, in response to an article in

Forest & Bird, 16 stout members offered to join a weka-breeding team. They surveyed weka, helped catch birds, attended meet-

ings, built large, weka-friendly aviaries, and with gusto set out to raise more birds. Quite quickly we learnt the first fallacy: that weka are easy to breed. ‘Just like chooks, a wildlife expert told us.

No, they’re not, as any weka knows. The breeders tried everything. They furnished their aviaries with logs, ponds, native plants and compost heaps, trying to create Utopia for weka. They provided their birds with special food, supplements, a weka-next-door, and weka calls from tape recorders. Letting the young females ‘eye up the talent’ scientifically called ‘flock mating, produced weka couples who filed for divorce as soon as they got in the breeding aviary. We tried everything to encourage our weka pairs to breed. And although a few did, nesting and rearing their chicks, most didn’t. In the end we

simply released weka which failed to breed and replaced them with new pairs of cap-tive-bred young birds until we found partnerships that worked. It was a long, slow grind, but eventually the group bred 52 young birds in a season. Karangahake Gorge which cuts through the Kaimai Range between Thames Valley and the Bay of Plenty. After trying to interpret the factors behind the collapse of the Gisborne weka population, we sought criteria for the best place to release our young weka. We looked for a place free from drought, with a mixture of native forest and farmland, wetland and weeds, to provide cover and feed for weka all year around. The place we chose was on the property of successful weka breeders the late Gary Staples and Elaine Staples, near Kaimai Conservation Park. Here the weka team built a weka "boarding school’ to accommodate captive-bred young birds until they were mature enough to release. The young birds were kept in groups in the aviaries for at least six weeks, and then the door was opened. They didn’t go far, held by the familiar site and the calls of those birds still in cages, so we avoided the dispersal and loss that had been the undoing of earlier releases straight into the wild. For five years weka were released in the Z or their release we chose a site in the

Karangahake Gorge. Some wore radio transmitters to assist monitoring and Gary scrambled through gorse bushes checking on them. Once, a dog took a terrible toll, until we found it a new home. In the spring of 1995, adults with chicks were seen in the wild. Then disaster struck. In less than a week most of the wild weka disappeared. Some were found as bloody corpses. We used their bodies as bait to trap their predators — two ferrets, one a pregnant female. The fledgling weka population had been annihilated and so almost, it seemed, were the weka team, who had put such effort and devotion into their birds. Sadly, we had discovered a second fallacy: that weka could withstand predation. No. Weka don’t stand a chance against a dog or a ferret. We'd heard stories of weka driving away or even killing stoats, but now we know that it is usually the weka that is killed. Drought and starvation may have precipitated the collapse of the weka population in Gisborne, but it is predators like stoats that are finishing off the remnant groups; just as it is predators that would destroy any such fledgling populations as our weka team could release. his was a blow to our hopes of reestablishing weka on the mainland. It seemed predator-free islands were the only option left. Yet finding an

From more than 88,000 birds in the early 1980s, East Coast weka numbered less than 5000 in 1991. Now there are less than 700 left on the mainland.

Weka on Islands lightless, but good swimmers, i- weka didn’t occur naturally on small islands far from the mainland. When, in earlier days, people put them on offshore islands, the weka ate lizards and killed vulnerable, ground-nesting birds. DoC has removed weka from some islands where they are deemed to threaten more endangered species: Stewart Island weka were killed or repatriated from Codfish Island, now home of the kakapo. Now the Stewart Island weka is almost extinct on Stewart Island itself and restricted to a number of smaller islands. The buff weka, once widespread in Canterbury and North Otago, was introduced to the Chatham Island. There are no stoats or ferrets on the Chathams so there the weka thrives, although it is now extinct in the South Island. Its good fortune has not been shared by the _ taiko (magenta petrel), and _ other Chatham Island birds, which are preyed on by cats, rats, possums, hedgehogs, pigs, hawks and weka. DoC is fencing the taiko breeding area to exclude cattle, and is trapping introduced mammals and weka. North Island weka survive on Kawau Island in the Hauraki Gulf, introduced there by an early governor, Sir George Grey. He was an animal fancier, not a conservationist, and introduced many animals from other countries to Kawau Island. His legacy includes four species of Australian wallabies which nibble any hope of regeneration below the few native trees, which are also browsed by possums, living in a forest of kanuka, acmena, pine trees and arum lilies. The North Island weka he introduced survived for half a century before dying out and being re-intro-duced by the Wildlife Service in 1976. Today Kawau Island supports more than 70 percent of the North Island weka population. It is a welcome though precarious refuge for weka, and would be much more secure if the wallabies and possums were exterminated, incidentally reversing the botanical degradation of this sad island.

island was easier said than done. Weka are predators themselves, and not always welcome on islands where they would not have been found in the past. Despite the bird’s threatened status, no DoC-managed island has been made available for weka and instead we had to rely on the generosity of private island owners. The first island weka home was Pakatoa, owned by the Ramsays, where we released 29 weka in 1996. The chief drawback of Pakatoa is its tiny size; only 24 hectares, and half of it is golf course! Yet the weka thrive. The guests to the island resort find them charming (and many think they are kiwis). After the release, numbers quickly rose to 50 or more birds, and then just as quickly fell in a summer drought. Then, 1999 was a warm, wet year and weka numbers rose again to 80, so in December the weka team caught 10 juvenile weka and transferred them to Whanganui Island, the site of our next release. Whanganui Island, owned by the Spencer family, lies just offshore from the town of Coromandel. At 283 hectares, it is a big, farmed island, with regenerating native forest and pine plantations. Its major drawback is that a stoat or ferret could swim across from the mainland. The first captive-bred weka were released on the island in 1997, and many probably fell victim to stoats and hawks, attracted to the island by the numerous rabbits. However by 1998 calicivirus had decimated the rabbits so fewer hawks were about and the stoats had been trapped. More weka were released and since early 1999, weka numbers have been increasing.

Upper Coromandel Forest and Bird, and the farm manager Kim Ward, maintain traps and bait stations on the mainland and on the island to try and keep the island stoat-free. Kim’s surveys in April this year indicate that there are at least 28 and probably up to 40 adult weka on Whanganui Island, many in pairs and spread all over the island. This is very promising and suggests that, if we can keep the island free of predators, it will become home to a large and important population of the North Island weka.

eanwhile, back on the East Coast, weka groups around Gisborne continue to fragment and decline in the classic pattern preceding extinction. Yet revived populations have appeared in the well-watered hinterland in the Toatoa and Whitikau valleys. Here DoC has based an officer to monitor the birds and trap stoats, ferrets and wild cats. Recently the weka protection work has extended into the Motu valley where

predator control is expected to benefit kiwi, blue duck, and other species, as well. While the increase in weka numbers in the Toatoa and Whitikau valleys is good news, it appears to reflect the present scarcity of mustelids (ferrets and stoats) there. However the past two winters have been mild with plentiful fruit on the native trees. Rat numbers are rising and the fear is that mustelids may appear in pursuit. Mustelids are numerous in the Motu area with 62 stoats trapped last summer. These small weka populations are all that are left on the mainland. If they can survive with DoC’s help, then the North Island weka may not yet become another species entirely marooned on islands. Forest and Bird’s weka project failed to establish a new, mainland population of the threatened North Island weka, but it has achieved many things. It has drawn attention to the weka’s plight and learnt useful techniques for captive breeding, information which is recorded in a "Weka Husbandry Manual’ Best of all, the project has established a small weka population on Pakatoa Island, a growing population on the larger Whanganui Island, and provided weka which will soon be released in the Karori Wildlife Sanctuary near Wellington. These populations will nudge the North Island weka a little further back from the brink of extinction.

New Zealand Weka Ts are four subspecies of the endemic weka. North Island weka are found in the Gisborne district in the Toatoa, Whitikau and Motu valleys which hold about 650 weka. It also occurs on a few islands: Kawau, where weka numbers are approximately 3700; Rakitu (Arid Island off Great Barrier), 135; Mokoia (in Lake Rotorua), 100; Pakatoa (Hauraki Gulf), 80; and Whanganui (off Coromandel), 28 to 40. Western weka live in Marlborough, northwest Nelson and mid- and northern West Coast. Their numbers fluctuate but this is the most numerous weka subspecies. Buff weka were peculiar to the eastern.South Island where they became extinct about 1924. Introduced to the Chatham Islands in 1905, they are currently numerous on Chatham and Pitt islands. DNA study suggests the buff weka may be a colour variation of the western weka. Stewart Island weka are practically extinct on Stewart Island but survive on some nearby islands.

Mainland islands n each of its conservancies, DoC is trying to create a ‘mainland island’ — an : area where intensive pest control provides a relatively predator-free sanctuary. At Karori Wildlife Sanctuary, near Wellington, and at Turihaua, north of Gisborne, similar but smaller ‘islands’ are being achieved by pest-proof fencing. The weka team has provided North Island weka for both Karori and Turihaua and hopes that in time, weka will be re-established in most of DoC’s mainland islands.