22 Jun 2016

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Sooty shearwaters, also known as mutton birds, are making a comeback in a remote Banks Peninsula breeding colony.

A headland at Stony Bay, about 10km from Akaroa, is one of the last remaining Sooty Shearwater or Titi breeding sites in the South Island. Monitoring from the recent breeding season has shown the number of young has grown to 38, a significant rise from last year's breeding season when 27 were counted.

The increase is a sign that efforts made to control predators are paying off, says Paul Devlin, a Banks Peninsula Ranger for Christchurch City Council.

The Council helped build a huge predator-proof fence around the colony in 2010 as part of a joint project with the Department of Conservation and the Banks Peninsula Conservation Trust. The fence encloses about half a hectare of land on the edge of high cliffs.

Mr Devlin says before human habitation there would have been huge colonies of shearwaters, and other native bird species such as mottled petrel and fairy prions. With the arrival of people and introduction of predators, many of these species have become extinct on the Peninsula and the sooty shearwater colony - which can be seen by walkers on the Banks Peninsula Track - is the last one remaining in the area.

Council Senior Field Ranger for Port Hills and Banks Peninsula Phil Crutchley says with the predator proof fence doing its work, the colony is slowly recovering, and there are currently about 60 breeding pairs.

“From the low of five active burrows in the early 2000s there are now 38 chicks ready to fledge after the 2016 breeding year. It’s hoped that in the not too distant future there will be hundreds of Sooty shearwaters returning to the wild from this colony.

“Seabird colonies are vital ecosystems that bring in large amounts of nutrients back to the land, which has a carry-on effect for local flora and fauna. That’s really been missing from the mainland for about 100 years. And it’s great to have these birds coming back to an area where they used to live.”

In the 1990s local Stony Bay landowners Mark and Sonja Armstrong were concerned with the declining sooty shearwater population and they built their own exclusion fence to keep predators out. Unfortunately stoats were still finding their way through the fence and by 2001 the population was down to five active burrows.

The Armstrongs approached DoC for help and a plan was put together to build a new fence with Christchurch City Council contributing funding.

Sooty shearwaters are seabirds that can live in flocks of tens of thousands, particularly around the southern South Island and Stewart Island. Also known as muttonbirds, the young are harvested at traditional sites around Stewart Island by Rakiura Maori.