Parks Canada is instituting a 'death from above' attack on the rats that have taken over at least 18 islands in the Haida Gwaii archipelago.

Laurie Wein, a project coordinator with Parks Canada, says that starting in September, her team will launch an aerial attack on Murchison and Faraday islands, dropping rat poison from the sky.

"You use a bucket that's suspended below a helicopter and distributes the bait," Wein said.

Wein says the Norway rats and black rats are invasive, and likely arrived on the islands sometime in the late 1700s, around the same time ships from Europe began sailing into the area.

Since then, the rats have multiplied and spread out across many islands in the Gwaii Haanas National Park Reserve, where they have nearly wiped out some seabird populations.

Of particular concern to Parks Canada's conservationists is the ancient murrelet, a bird that nests in underground burrows. The ancient murrelet was nearly wiped out on Haida Gwaii a few years ago, Wein said.

"Rats arrive on these islands and they eat the eggs of seabirds," she said. "They eat the young chicks."

Ground-based attack a success

Two years ago, Wein and her team set out ground-based bait stations on the Bischof islands and Arichika Island, which are much smaller islands.

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An ancient murrelet chick. (Jake Pattison/Laskeek Bay Conservation Society/Parks Canada)

In order to minimize the impacts of the poisoning campaign, crews went around and gathered up the carcasses of the rats that died outside their burrows. No evidence of rats was found at the end of the three-month program in November 2011, nor were any rats detected in the spring of 2012.

Since then, the bird populations on those two islands have started to bounce back, Wein said.

Wein said similar anti-rat aerial attacks have been carried out on islands around the world, including the Galapagos, but this is the first time Canada has used aerial eradication. The aerial attack strategy might sound drastic, but Wein says success relies on 100 per cent coverage.

"You need to remove all rats. You can't leave rats behind, obviously, because rats are so... they're such quick reproducers," she said. "They can quickly rebound... in terms of their population, and start having those detrimental effects again."

Wein said the ultimate goal is to get rid every last rat on Haida Gwaii.

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In 2011, a rat-eradication program was launched on the Bischof Islands (in foreground), which form part of the Gwaii Haanas National Park Reserve. (Andrew Wright/Parks Canada)

With files from the CBC's Marissa Harvey