Robins flourish, dawn chorus returns to the Mt Aspiring National Park

Marjorie Cook / STUFF.CO.NZ

Matukituki Charitable Trust volunteers Heather and Stu Thorne explain the predator control programme credited with helping native robins thrive at Aspiring Flat.

Two decades ago, Wanaka couple Stu and Heather Thorne would eat their breakfast porridge at Aspiring Hut in almost complete silence.

Now, the dawn chorus is a noisy morning wake up call, with breakfast an extra rowdy affair if clownish keas decide to drop by and chew on the doormat.

Birds are back in abundance, thanks to a predator-trapping and bird-banding programme the couple have been spear heading for the Matukituki Charitable Trust.

Stu and Heather Thorne outside the warden's hut at Aspiring Flat.
MARJORIE COOK

Stu and Heather Thorne outside the warden's hut at Aspiring Flat.

"Before, it was almost non-existent. Now we have got birdlife everywhere," Stu said.

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Stu put in the first predator traps near the historic stone tramping hut in 2000, when he was working as the Department of Conservation's biodiversity manager in Wanaka.

Ground-grubbing South Island robins are thriving at Aspiring Flat.
D Lousley/southernlight.co.nz

Ground-grubbing South Island robins are thriving at Aspiring Flat.

There were 24 traps in all and about seven years ago - a year before he retired from Doc - Stu had enough kills under his belt to confidently release 25 South Island robins at Aspiring Flat.

The robin is not threatened and there were plenty in the Routeburn Valley. But thanks to the unappeasable appetite of bird-munching stoats, rats, mice, cats, hedgehogs and possums, there were none left at Aspiring Hut.

Three seasons ago, the Matukituki Charitable Trust revived Stu's battle for the birds and now there are 600 traps and the robins are flourishing.

A juvenile male native south island robin at Aspiring Flat.
MARJORIE COOK

A juvenile male native south island robin at Aspiring Flat.

The dark grey, white-breasted birds stand about 18cm tall and weigh 35 grams but hold their own in any bird choir, sustaining loud, descending phrases of "pwee-pwee-pwee".   

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Stu now works part-time for DOC as Aspiring Hut warden - a role he shares with environmental photographer, Donald Lousley.

The hut is about 50km drive from Wanaka and another 10km tramp from Raspberry Creek.

Heather Thorne uses a generic bird caller to attract robins.
MARJORIE COOK

Heather Thorne uses a generic bird caller to attract robins.

​Heather, a former Lake Wanaka Tourism administrator, has joined her husband in retirement and devotes many voluntary hours to the trust, building on the work Stu started many years ago.

"The numbers [of robins] didn't build up for a few years. But now we've got a wee bit behind in the banding," Heather said.

The trust's success story gives some hope that the Government's Predator Free 2050 campaign can go a long way towards achieving its ambitious goal of ridding the country of possums, rats and stoats in just 34 years.

A generic bird caller will attract many sorts of birds. It works by twisting the key on the right.
MARJORIE COOK

A generic bird caller will attract many sorts of birds. It works by twisting the key on the right.

In July, the Government stumped up $28 million to be spent over on the campaign over the next four years. It also wants to match every $2 of private and local authority input with another $1.

The Thornes agree the goal is challenging but they're giving it a crack because the other option, no birdsong, is too sad to contemplate.

"In this valley here, we only have 600 traps. On Secretary Island they have over 2000. The logistics of that is mind boggling and there is work going on down there on other islands at the same sort of intensity," Stu said. 

A baby rat is caught in a trap in the Mt Aspiring National Park.
MARJORIE COOK

A baby rat is caught in a trap in the Mt Aspiring National Park.

Conservation corridors of pest free habitats is one way of fighting pests on the mainland. Surely natural alpine barriers also play a part in keeping predators from the remotest parts of the Mt Aspiring National Park?

Not so, say the Thornes.

"The problem is that stoats are being seen in alpine areas. They will just go over the Cascade Saddle . . . A stoat at Makarora was tagged once and it was seen at the Haast Pass and the next day it was back at Makarora," Stu said.

This type of "trapinator'' is baited with peanut butter to catch possums.
MARJORIE COOK

This type of "trapinator'' is baited with peanut butter to catch possums.

The trust's Wanaka-based trappers are now climbing mountains to lay ever more gnarly lines to cut predators off at the pass.

"The likes of a stoat - it is just a survivor . . . They are just a cunning animal. Until we get a biological control, we are not going to win," Stu said.

Fortunately, trampers don't need to go high to see the trust's work. Some traps are visible along the gentle 10km route from Raspberry Flat.

A possum makes his last tree climb in the Mt Aspiring National Park.
D Lousley/southernlight.co.nz

A possum makes his last tree climb in the Mt Aspiring National Park.

Stu has DOC's okay to check one trap line for the trust while he is on hut duty but his primary role is to take hut fees, provide tramping information and check the trails between Aspiring, French Ridge and Liverpool huts and the Cascade Saddle.

Heather regularly joins him for several days during his 10-day shifts to check traps and help band robins.

The robins dine on invertebrates and are easily caught on the ground with a long-handled ground net.

Volunteers have discovered this Goodnature trap can cause a pile up of mice on the forest floor, providing a free ...
MARJORIE COOK

Volunteers have discovered this Goodnature trap can cause a pile up of mice on the forest floor, providing a free "take-away'' service for larger predators.

"They do have territories, but if you feed them they will follow you for miles in the bush, sometimes the distance of two traps," Heather said.

Heather uses two bird-calling devices to call in the naturally curious robins.

One, a generic caller, uses a high-pitched distress call that all birds recognise and investigate and Heather has discovered robins, the rifleman, and tomtits appear quickly but the chaffinch and the grey warbler are not first responders. 

A Department of Conservation predator trap near Cascade Hut.
MARJORIE COOK

A Department of Conservation predator trap near Cascade Hut.

The other caller is a recording of robins. "With the recorded sound I found the birds were getting quite testy so I got another one they found more acceptable," Heather said.

Heather is not an ornothologist; she just loves being out in the bush and noticing changes in the robin population.

"I got into it because Stu bought them over. They just existed here and then they suddenly exploded. It's great to have the positive story. We are always hearing about things slipping, so it is so nice," she said.

Baited tracking tunnels are used to take footprints of predators, helping volunteers get an idea of how many predators ...
MARJORIE COOK

Baited tracking tunnels are used to take footprints of predators, helping volunteers get an idea of how many predators are around a particular area. They are not traps.

The traps weigh about 15kg each and include humane traps that hold live wildlife - perhaps an indignant kea - until Heather or Stu can release them.

Others offer sudden death experiences, such as the peanut butter-baited "trapinators" attached to tree trunks.

It can take Heather about half a day to check a trap line, which are all on GPS. They lines from flat and easy to hard and high.

One of the many kakariki that have flocked to Aspiring Hut.
Maggie Evans

One of the many kakariki that have flocked to Aspiring Hut.

She also checks up to 16 baited tracking tunnels, which take footprints to provide information about what predators are about. Last time she checked them, just five of 160 footprint cards had no foot prints.

DOC's 150, 200 and 250 traps (the numbers relate to the width of plate they stand on) go off just the once and have to be regularly cleared. Newer technology is represented by the Good Nature "trapinators".

The A24 is usually set low on a tree trunk to catch mice, while the A12 is set higher to catch curious stoats and possums.

Nature dealt to this mouse found on the track to Aspiring Flat.
MARJORIE COOK

Nature dealt to this mouse found on the track to Aspiring Flat.

The numbers refer to the shots contained in the trap's gas cylinder - for example, the A12 is able to reset itself 12 times.

The trust buys thousands of chicken eggs every year to bait the traps. It also uses "rabbit paste" - a cheap, salty substance rendered from dead rabbits.

Although the predators love eggs, there is debate over how effective egg bait is compared to salted rabbit.

"There has been quite a lot of talk about it," Stu said. "They tried to replace them with golf balls,"

"But possums don't play golf," Heather quipped.

"Bait and lures are the big problem with traps. If you resetting traps, they are still only as good as the bait. There is research going on in New Zealand to try and get a long-lasting bait," Stu said.

Heather has found eggs last longer in the winter but rabbit paste will go mouldy.

"Way back in the day, I used Fenn traps on Roy Roy [track] but people were setting them off and throwing them away. We don't get so many problems these days. But we still get a lot of enquiries about what we are catching. There is still not a good understanding of how much damage these pests will do," Stu said.

Kea also tamper with traps. The native parrots have worked out if they peck around the screws they can eventually rip off the lid. Metal plates have stopped that.

About two years ago a 18-strong gang of noisy juvenile keas invaded Aspiring Flat and bothered campers from midnight to dawn with their burgling antics.

Every night, they stomped around on the deck of the warden's hut, attacked the doormat and ate the rubber door seal.

But many have now moved on, for reasons the Thornes can't truly explain. Heather suspects they flocked to Treble Cone to bludge a feed from skiers.

Late last year, trust project manager Paul Hellebrekers estimated the lives of an estimated 47,000 wildlife had been saved by killing 911 predators in seven months.

It is not just the ground-grubbing South Island robins that have flourished.

Flocks of kakariki, a native parakeet, are now abundant.

"Before, we would only see two or three right in the canopy, but now you might find 10 on a branch," Heather said.

 - Stuff

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