A helping hand for Hutton's shearwater

DEIDRE MUSSEN
Last updated 05:00 14/03/2012
GOT EM: DOC biodiversity project manager Phil Bradford with an endangered Hutton's shearwater chick to be moved from its mountain home high in the Seaward Kaikoura Range.
DAVID HALLETT/Fairfax NZ

GOT EM: DOC biodiversity project manager Phil Bradford with an endangered Hutton's shearwater chick to be moved from its mountain home high in the Seaward Kaikoura Range.

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Catching Hutton's shearwaters is hands-on. Or more like arms in.

You plunge shoulder-deep into the labyrinth of muddy burrows on tussock-covered mountain slopes, feeling for a disturbed chick's indignant peck.

"I've got a beautiful chick in here," exclaims Conservation Department biodiversity programme manager Phil Bradfield.

He carefully extracts the squawking ball of grey fluff and measures its wing length to check if it is a suitable age – that it will fledge in a few weeks. "A lot of people think bird work is glamorous," Bradfield jokes, his arms covered in mud.

Fellow chick collector Mike Bell, operations manager for Wildlife Management International, agrees. "Your arm gets scratched to bits, there's mud everywhere but we love it."

Over three days last week, the pair plus Marlborough contractor Dave Barker collected 102 chicks from high in the Seaward Kaikoura Range.

Packed in cardboard carry boxes, they are airlifted by helicopter to a man-made colony on Kaikoura Peninsula, only minutes from the touristy seaside township, to boost numbers already there.

"This [relocation] is possibly the most publicly accessible in the world," Bell says.

When these endangered seabirds fledge, the location of their new home will be imprinted on their birdbrains. In about three years their internal navigation will guide them back there to breed.

Hutton's shearwaters' population is estimated at 420,000 birds with 106,000 breeding pairs at the head of the Kowhai River catchment and 8000 breeding pairs on Puhi Peaks Station, about 10 kilometres north in the same mountain range.

That there are only two breeding colonies worldwide makes the bird vulnerable to extinction.

Historically, other birds were their only predators, but human impacts, such as fires and hunting, plus introduced pests and predators, have destroyed many colonies.

Of eight colonies found in the mid-1960s in the Seaward Kaikoura Range, their sole refuge nationwide, only two remained by the early 1980s. Anecdotal evidence indicates pigs wiped out the other six colonies, digging up burrows and gorging on chicks.

"The theory is these two colonies have survived as it's so gnarly to get in and pigs haven't found their way in yet," Bradfield says. "It would be like a picnic for a pig here. They would scoff the lot."

Goats, deer and chamois damage underground burrows while traversing the fragile terrain. The tracks they create potentially allow pigs to enter.

Possums, rats and hedgehogs are other predators.

Stoats have large home ranges and defend them from other stoats, therefore only a handful live in the crammed shearwater colony, having minimal impact on their numbers.

In 2005, a trial was started at the Kaikoura Peninsula to create a founding population. About 12 chicks were placed in wooden burrows, with plastic pipe exits, dug into the grass-covered hillside.

Over the following three years, 273 chicks were relocated there from the Kowhai colony, but success was marred due to cats killing many birds.

Urgent action came in the form of the Hutton's Shearwater Charitable Trust, established in late 2008.

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It raised $300,000 to erect a predator-proof fence to protect the peninsula colony.

The chicks relocated last week are the first to live behind the predator-proof fence.

In the past few years, a handful of breeding pairs have returned to the man-made colony but early breeding by the young birds has been fraught, Bell says.

This year, four pairs laid an egg each but only one hatched – a major breakthrough. That chick will fledge in a few weeks, then migrate to the Timor Sea, via Australia, to winter.

Bell says the 102 chicks relocated from the Kowhai colony last week are an important boost to ensure the peninsula colony's long-term survival.

Next year, a further 100 chicks will be shifted there from their mountain home.

Typically, pairs return to their colony in late August to mate and prepare burrows.

Egg laying starts about a month later, with one parent sitting on the nest for five to 10 days while the other feeds at sea.

After about 50 days, the eggs hatch and chicks take three more months to fledge. The parents leave their chicks alone in the burrow during the day while they forage at sea, to return at night to feed them half-digested fish which they regurgitate.

Chicks become 25 per cent heavier than parents butstart to lose weight a month before they fledge, putting most of their energy into growing feathers and muscles. In the final week, or so, they stop eating to lose weight and start practising to fly.

Bell says chicks get no parental help in learning to fly and fish. Many die in the first year, most in the few weeks, with fatter chicks having greater survival odds.

However, a seven-year study into breeding success has shown an improvement in the odds over the past three years.

"We suspect it's about what is going on out to sea," Bradfield says.

One possibility is a set-netting ban off the east coast, introduced in 2008, although it has recently been relaxed by the Government.

"There are lots of horror stories of netting Hutton's shearwater. You don't just catch one, you might catch hundreds," Bell says.

Barker agrees, saying many chicks high on the mountain die of starvation as a result.

Last Thursday evening, the last 50 chicks are flown to the peninsula.

A full moon rises out of the sea as the last chick is nestled into its artificial burrow.

"It's a positive sign," Te Runanga O Kaikoura representative Brett Cowan says. The shearwater are a taonga species, and historically were an important food source for Maori.

Over coming weeks, a team of seven feeders, including Barker, will give their charges "sardine smoothies" until they launch into the world, taking with them the hopes for a new community.

Farewell celebrations for the departing fledging birds will be held on March 31 and April 1 in Kaikoura.

As Bell says, the new 2.4-hectare peninsula colony has enough room for tens of thousands of Hutton's shearwaters.

These special seabirds will get all the help they need from the trust and supportive community to transform the peninsula from barren farmland to a rich Hutton's shearwater colony bulging with life.

- The Press

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