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New Zealand Rock wren thriving on new sanctuary

13/04/2010 07:52:12

New Zealand Rock wren, by Steve Horn.

Secretary Island - First Safe Haven for Rock Wren

April 2010. Finding twelve tiny unbanded birds on the highest peaks of Secretary Island in Fiordland has signalled an exciting development in the fight to save the vulnerable alpine rock wren. A search by four Department of Conservation (DOC) rangers earlier this year revealed the unbanded rock wren, confirming that birds relocated to the island over the past two years have successfully bred.

Successful relocation
"This is the first time rock wren have ever been successfully relocated to a location free of introduced predators," said Megan Willans, DOC ranger in Te Anau. "We put leg bands on the twenty-five birds transferred to the island over the past two years, so finding this many unbanded birds means they have settled and are breeding, We plan to transfer a further 15 birds this year to ensure a robust start-up population."

New Zealand Rock wren
Rock wren are the only true alpine birds in New Zealand, spending all their lives in rocks and scrub above the bush line. Not many off-shore islands are suitable for these tiny birds, but Secretary Island, the third tallest island in New Zealand, offers the sort of harsh alpine areas they seem to prefer. Rock wren are threatened by introduced predators in their homes high in the mountains. A study in Fiordland's Murchison Mountains showed their population almost halved over the twenty years between 1985 and 2005.

It is unknown how many rock wren are left on the mainland, but anecdotal evidence suggest their range is shrinking and they are no longer found in many areas where they were once common.

New Zealand Rock wren

Rock Wren are one of the most ancient bird species in the world, possibly stemming from a species present 82-85 million years ago when New Zealand and Australia separated from the ancient Gondwana landmass. There were once at least seven species of wren in New Zealand, of which only two still survive; rock wren and their bush relatives the riflemen. The bush wren and the Stephens Island wren died out since European colonisation of New Zealand. The Stephens Island wren was wiped out by the lighthouse keeper's cat..

  • Secretary Island is 8140ha and has never had established rodent or possum populations making it ideal to target for conservation restoration.
  • A further fifteen rock wren will be transferred this year to bring the founding population up to forty birds, which is considered to provide an appropriate genetic basis for a new population of birds
  • In 2004 a network of over 120km of tracks were cut on Secretary Island in preparation for the stoat and deer control programmes. 940 wooden and wire mesh trapping tunnels were established across the whole island and stoat trapping began in 2005. Intensive deer control is also underway and 496 deer have been removed from Secretary Island since October 2006

South Island Robin and Mohua
In addition to the unbanded rock wren found on Secretary, the DOC team also sighted unbanded Mohua and South Island Robin. South Island Robin were transferred to the island in 2008 in the first project sponsored by the Fiordland Conservation Trust. The transfer of Mohua to the island was yet another project sponsored by BDG Synthesis.

Pest removal
Department of Conservation Area Manager, Reg Kemper of Te Anau said that the successful breeding of birds that had been transferred was significant as it was the fruit of all the earlier restoration work focused on removing stoats and deer from Secretary Island. "The island is beginning to be the safe haven for threatened bird species that we dreamed it could be."

Saving the rock wren is a flagship conservation project for BDG Synthesis, a Wellington science research company. Despite initial setbacks with establishing an island population BDG Synthesis have continued to support rock wren research and the attempt to establish a secure island population.

"We hope that we are wasting our money and that the situation is not as dire as many are saying, but this bird could disappear very quickly without the vision and tenacity of Megan Willans and the team at DOC," says Barry Dent, CEO of BDG Synthesis.

"Rock Wren are tiny birds, so they are very vulnerable to predation. Even mice eat their eggs and chicks on the nest," said Ms Willans. "Their populations are declining on the mainland, so it is important that we establish populations in predator free areas. We are confident they will do well on Secretary Island."

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