An airborne assault will begin this fall in the ongoing war to rid important bird-nesting islands of non-native rats in Gwaii Haanas National Park Reserve.

As part of a five-year, $2.2-million program, officials will employ a helicopter to drop rat poison over two sites in Juan Perez Sound: 400-hectare Murchison Island and 316-hectare Faraday Island.

At-risk species such as ancient murrelets have vanished from their nesting sites there over the years due to the rats.

Thats the problem, theyre so voracious, Parks Canada project manager Laurie Wein said in an interview Wednesday. Theyll eat the eggs, the young chicks. They can have a dramatic impact on ground-nesting seabirds.

When the rats run out of birds, they turn to intertidal areas to forage on marine life. Theyll eat anything. Theyre not picky.

In the first phase of the program, in 2011, officials launched a ground-based program, placing poison bait boxes on two other islands 95-hectare Bischof and 10-hectare Arichika to eradicate the rats.

The results of that program are still being monitored.

We dont declare success until we know weve had two years where we cant detect rats ... but so far things are looking good, Wein said.

Due to the size of Murchison and Faraday, officials decided to opt for a more practical helicopter-based application. Its similar to agricultural seeding operations, a bucket suspended below a helicopter that dispenses a pelleted bait.

Wein does expect some accidental poisoning of other species including scavenging birds such as ravens. Monitoring shows that a native mouse and shrew are virtually gone from the islands, again due to the rats impact.

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Helicopter to drop poison to rid Gwaii Haanas islands of rats