Captive-reared New Zealand blue ducks released into a stoat-controlled region

From Stuff.co.nz:

The doors whip open and out they waddle, plunging into the rapids to test paddling skills before floating downstream to feed.

It is home time for eight whio, or blue ducks, more than three months after they were removed from their river-edge nests as eggs to be reared in Christchurch.

The nationally endangered species gets a helping hand around New Zealand, with efforts focused on eight “security sites”.

Yesterday was the fourth release of juvenile ducks at one of the West Coast sites – the Styx-Arahura-Taipo valleys near Hokitika – since the whio Operation Nest Egg project began there in 2006.

Intensive stoat trapping started in the area eight years ago to protect dwindling numbers of the rare waterfowl species, which prefers life in swift mountain streams and is endemic to New Zealand, with no close relative worldwide.

By 2004, only three breeding pairs remained in the Styx Valley, but the Solid Energy-sponsored project helped increase that to eight breeding pairs.

In September and October, eggs from two whio nests were removed from beside Doctor Creek, a Hokitika River tributary, helicoptered out of the mountains and driven by car to Christchurch to be incubated and reared at Peacock Springs Wildlife Park in Christchurch.

Curator Anne Richardson reared her demanding brood in enclosures over fast-flowing springs to ensure they developed good skills.

Yesterday, Press photographer Dave Hallett was thrilled to have the privilege of transporting the eight whio back to the West Coast.

“I’ve never driven that carefully in all my life,” he said.

“I was completely chuffed that the Department of Conservation had that much faith in me.”

Hallett, a bird enthusiast, followed the distinctive slate-blue birds from nest to release to document their progress, including capturing the surprising moment when one duckling hatched in Richardson’s hand only minutes after arrival at Peacock Springs.

Two of yesterday’s eight ducks, a pair, were freed near Greymouth, at the Moonlight Valley, to aid the Paparoa Wildlife Trust’s whio project.

The remaining six – three female and three male – were flown to the Styx Valley, a neighbouring valley to their birthplace.

Once common throughout New Zealand, now only about 2000 blue ducks remain, with the numbers of breeding pairs almost evenly split between the North and South islands.

The Conservation Department’s Hokitika biodiversity programme manager, Dave Eastwood, is “quietly optimistic” about the whio’s future, but also has fears.

“Rats and stoats are out of control. Even with trapping, they keep migrating into areas.”

New Zealand’s wildlife evolved without land-based mammalian predators.  New Zealand has native birds of prey, but it never had cats or mongooses or weasels or dogs or even rats running about until relatively recently.

New Zealand’s ground nesting birds, like these blue ducks, never evolved good nest hiding behavior, which makes them quite vulnerable to predators.

European rabbits and hares were introduced to New Zealand as game animals, and because they also did not suffer from any land-based predators, their population exploded.

Stoats were introduced to control the number of rabbits and hares, but that’s kind of like releasing lions into high crime areas to control gangs. Yeah, the lions will control the gangs a bit, but gangs are armed. The lions are much more likely to attack people who have nothing to do with the gangs.

The rabbits and hares in New Zealand descended from ancestors who had long suffered stoat predation and had evolved defenses against them. The stoats do kill some hares and rabbits, but not enough to significantly reduce their numbers.

However, the stoats do a much better job killing these native New Zealand birds, which evolved without any sort of land-based predators. They have virtually no defenses against them.

I don’t know how long these New Zealand conservationists can keep the stoats at bay.  They are going to have to be constantly trapping them in order to keep them under control.

And they aren’t going to trap all of them. Stoats are carnivorans and are quite intelligent animals. Some are craftier than others. These crafty ones will avoid traps, and they will pass on their craftiness to their offspring– both in terms of their genetics and what the mothers teach their young.

Eventually, the only stoats that are going to be in that region are those that are really trap-wise, and then I don’t know what they will do to control them.

It may be a losing battle in the end.

But it is worth the fight.

Because it’s the only option.

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