Populations of the South Georgia pipit, the world’s most southerly songbird, have been devastated by an infestation of rats in the remote British overseas territory.
Now workers from a Dundee-based charity undertaking the world’s largest rodent extermination scheme have found a nest holding five of the rare chicks in an area of South Georgia previously over-run with rats.
South Georgia has no resident human population but its inhospitable sub-Antarctic environment supports an abundance of marine and terrestrial wildlife.
But it had lately become over-run by rats, a non-native species brought in on whalers and other ships visiting the island since it was claimed for Britain by Captain Cook in 1775.
“The discovery of pipit chicks is thrilling news and shows the rapid beneficial effect of the Habitat Restoration Project on this threatened species,” said Alison Neil, chief executive of South Georgia Heritage Trust (SGHT).
“People had spotted pipits exhibiting breeding behaviour following the baiting work, but this is the first firm proof that they are nesting in areas from which they were previously excluded by rodents.
“Pipits cannot breed when rats are present, so this discovery is confirmation that birds are quickly responding to their absence.
“We are confident that when South Georgia is once again free of rodents it will regain its former status as home to the greatest concentration of seabirds in the world.”
The nest was spotted at Schlieper Bay, near the western end of the island, by award-winning polar researcher and former ‘Team Rat’ member Sally Poncet during an expedition to study albatrosses.
South Georgia was previously governed as part of the Falkland Islands Dependencies, but the territory of South Georgia and the South Sandwich Islands was formed in 1985.
Argentina laid claim to South Georgia in 1927, a factor that came into play during the 1982 Falklands War, when Argentine forces briefly occupied the island.
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The country continues to claim sovereignty of the territories.
Once a centre for the sealing and whaling industries, South Georgia also acted as a gateway to the Antarctic for explorers including Sir Ernest Shackleton.
SGHT’s £7.5 million habitat restoration project aims to reverse ecological destruction wrought by invasive rodents shipped to the wildlife oasis by whalers and other ships over the past 200 years.
The effects of climate change have also been causing the retreat of glaciers, allowing the rats to access new areas and gain an ever stronger foothold on the remote island.
Successful trial extermination schemes carried out in 2011 and 2013 suggest rats were wiped out from almost two-thirds of South Georgia.
The latest phase of the project, which is on a scale five times larger than any other rodent eradication attempted worldwide, aims to spread 95 tonnes of poisoned bait by helicopter over an area of 364 square kilometres.
The pesticide makes rats sensitive to light, causing them to retreat to their lairs to die.
This saves the landscape being left strewn with millions of rotting carcasses.
The challenge is to complete baiting of the entire island during the brief sub-Antarctic summer months. If successful, and no signs of rodents have been discovered by 2017, South Georgia will be declared free of rodents for the first time since humans first came to the island more than two centuries ago.
The Habitat Restoration Project has been funded by donations raised by SGHT and its US counterpart Friends of South Georgia Island, which have together so far raised some £6.6 million of the £7.5 million needed to complete the eradication project.