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The return of saddlebacks (tïeke)

10 December 2004

Standfirst: The return of saddlebacks (tïeke) to Boundary Stream, Hawke’s Bay, is only possible because of years spent developing pest control methods at the “mainland island”.

TIEKE calls are sounding again at Boundary Stream, an hour’s drive inland from Napier. If successful, the reintroduction will be a conservation first for the striking, native bird.

In moving North Island saddlebacks from a Coromandel island to the 800 ha native forest reserve, the Conservation Department is testing whether its pest control is good enough to protect tïeke, a bird that disappeared from the mainland in the mid-1800s.

At stake is the future of “Moa’s Ark”, the name that English botanist David Bellamy coined for New Zealand and its unusual wildlife.

The list includes our wattlebirds (tïeke, kökako), large flightless birds (kiwi, käkäpö, takahë), the world’s only alpine parrot (kea), whio - one of two torrent ducks worldwide, the stitchbird, wëtä, tuatara, a diverse lizard and land snail fauna with alpine species among them, native frogs lacking a tadpole stage, and the short-tailed bat.

“Many of these iconic species are in decline nationwide, even though we are helping populations rebuild at some places,” says Alan Saunders who pioneered the concept of protecting birds on the mainland.

“Mainland ‘islands’ are the spearhead of our conservation efforts, where we have shown that we can control several pest species at the same time, that we can measure the results, that we can protect and recover native species like kökako on the mainland. The question is whether we can control pests to low enough densities on an ongoing basis to allow tïeke to survive and thrive.”

At Boundary Stream, 70 stoats and 93 cats were trapped in 2003-2004. Kererü now number close to 4000, up on 3400 the previous year, and kiwi, 21, up on 14 a year ago.

Results like these give confidence for bringing back tïeke, says Ken Hunt, DOC Napier Area manager. Yet, Boundary Stream has had its share of setbacks. Only two pairs of five kökako in captivity bred in the last year, and an adult and a juvenile have since died, possibly because of stoat predation. Robin numbers there have not been increasing.

“We can get predator numbers down to very low levels but we cannot stop them walking into the reserve. The idea is to limit the amount of time pests spend there before they get caught, which means some predation will always occur. One ferret killed five kiwi in a fortnight before it got trapped. Imagine how many tïeke it could have caught.”

There was the time of year the reintroduction occurred – when birds were gearing up for breeding and more likely to settle at Boundary Stream than disperse, but with a risk of acclimatisation problems in leaving warmer climes at sea level for late winter cold at 600m altitude.

Questions remain over the effects of hedgehogs and mice at Boundary Stream, and whether they would limit the carrying capacity of the forest for tïeke.

Tïeke eat insects and grubs, as do hedgehogs and mice which are tricky to control. Mice, being small, may never run into poison baits or traps, and hedgehogs usually avoid both. The larger insects and other invertebrates have not increased in abundance as much as anticipated with possum and rat control. Are hedgehogs and mice responsible for this, and, if so, how to control them, asks Chris Ward, a scientist with DOC’s East Coast Hawke’s Bay Conservancy.

While 190 hedgehogs were trapped in 2003-2004 at Boundary Stream, the real question is how many are left behind, he says. Research has shown that the reserve may contain up to 4000 hedgehogs some autumns before numbers drop off over winter. Removing 4 per cent of the population a year would have no impact. With each animal eating 200 grams of invertebrates a night, hedgehogs must impact heavily on this key part of the ecosystem.

Then there are the mice. DOC staff know that mouse numbers at Boundary Stream stay moderately high year round, thriving in the gaps between the bait stations which are spaced 150m apart to target mainly rats and possums.

There are lessons here for the guardians of Moa’s Ark. Where possums, stoats, weasels, ferrets, rats, cats, goats and deer are controlled to low densities - a costly proposition - the outlook is good for flightless birds, kökako, whio, frogs, bats, snails, and, potentially, tuatara. Tïeke are now being tested.

Other species are difficult to protect, for many reasons. Individual kea range over huge distances and live in areas that are relatively inaccessible to humans but not to stoats. Stitchbirds compete poorly against more numerous tui and bellbirds and often need supplementary feeding. Lizard populations are often thinly distributed over large areas.

Aware of the conservation challenges, the Government aimed in its 2000-2020 Biodiversity Strategy to “halt the decline in New Zealand’s indigenous biodiversity”. The task has been proving a major challenge. An inter-agency report to Ministers last year showed that DOC was doing well on offshore islands and at intensively-managed sites like mainland islands, but declines were continuing elsewhere.

“It is important that we extend the work done at intensively-managed areas to more than a few dots on the map, and keep up the research,” says Conservation Minister Chris Carter. “Developments in many areas are encouraging. We set up the five kiwi zones in 2000, for example. DOC is now putting Operation Ark in place, an emergency response system for predator plagues, initially at three South Island beech forest sites. ”

Mr Saunders says the mainland islands were the main inspiration behind the kiwi zones and Operation Ark, as well as dozens of private and community-based projects around New Zealand.

At Boundary Stream, the tïeke release has relied on huge local support for conservation, 393 volunteer-days in 2003-2004, and $30,000 sponsorship for the tïeke programme from British-based fruit exporter Empire World Trade, and Hawke’s Bay’s Hill Country Corporation.

“We will have to wait till the tïeke settle in and show signs of breeding this summer before calling the translocation a success,” Mr Hunt says.

“If we are lucky, any problems with weather, predators and competitors for food won’t affect the birds too much. In any event, Cuvier Island has reached its carrying capacity of tïeke and the population there produces 200 chicks a year, so even if things don’t work out here, we haven’t really lost anything. On the contrary, we will have learned more about tïeke and their conservation. Taking managed risks is what conservation is about.”

Footnote: Six mainland islands were set up with special funding in 1996: Boundary Stream, northern Te Urewera, Trounson Kauri Park in Northland, Paengaroa reserve near Taihape, Rotoiti in Nelson Lakes National Park and Hurunui in inland Canterbury.

Box: Tïeke (208 words) The tïeke (saddleback, Philesturnus carunculatus) is a medium-sized, black coloured forest bird with a distinctive chestnut patch on its back, and orange wattles on its throat. The birds are often heard before they are seen, the males having a range of calls.

By early last century, North Island and South Island sub-species were close to extinction, restricted to Hen Island off the east coast of Northland, and three islands near Stewart Island, respectively.

The North Island sub-species is now distributed over nine predator-free offshore islands and at Karori Wildlife Sanctuary in Wellington.

Tïeke are poorly flighted, spending much time on the ground searching rotten wood and leaf litter for insects and grubs, and in the forest understorey for the fruit of shrubs such as kawakawa and coprosma species. As a result, adults, juveniles, eggs and chicks are vulnerable to predation by stoats and rats, as well as ferrets and feral cats.

Tïeke, like kökako and the extinct huia, are members of the wattlebird family (Callaeidae), which is found only in New Zealand.

In Mäori tradition, Maui asked the tïeke to bring him cold water, when weary and thirsty from capturing the sun. The tïeke ignored him. Infuriated, Maui grabbed the bird with his heated hand, singeing its feathers.

Bernie Napp, DOC journalist


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