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Concerns for North Island kōkako on Secretary Island following a promising start

Date:  23 July 2013

Secretary Island, at the mouth of Doubtful Sound, is recognised as one of New Zealand's ecological jewels and presents a wealth of opportunities to further advance our knowledge in pest eradication methods and restoration in the Te Wahipounamu World Heritage Area.

The Fiordland Lobster Company board members were old hands in island restoration when they partnered with the Department of Conservation (DOC) to undertake a brave endeavour, to re-establish kōkako in Fiordland. The company funded the transfer of twenty-seven kōkako from the North Island down to Secretary Island during 2008-9.

In 2011 hopes of success were raised when two kōkako pairs and most excitingly one fully fledged juvenile were observed, proving that Secretary Island provided suitable habitat for North Island kōkako to breed. Following these findings Fiordland Lobster and DOC began planning the translocation of additional birds to boost the founding population.

Kōkako juvenile on Secretary Island in 2011.
Kōkako juvenile on Secretary Island in 2011

However, in 2013 an experienced kōkako search party were surprisingly unable to locate any kōkako on Secretary Island. DOC Ranger Megan Willans said, "At this stage we cannot categorically say there are no surviving kōkako on Secretary Island, however evidence suggests that sadly most of the birds have perished."

Fiordland Lobster Board member John Steffens said, "Fiordland Lobster invested significant financial, and emotional capital in this quest to bring kōkako birdsong back to Fiordland, and is as gutted by this apparent outcome, as are the DOC and iwi teams who shared this dream."

All partners were aware of the risks associated with attempting to translocate a species outside of its natural range, the purpose being to establish a population of North Island kōkako in Fiordland as an ecological surrogate for the once present South Island kōkako. Like the kereru and extinct moa, kōkako are important seed dispersers vital for the regeneration of our forests.

Most North Island kōkako populations inhabit relatively small forested areas in comparison to Secretary Island and so the island also provides the potential for a large population of the birds with approximately 4000ha of suitable habitat. Stoats are the only introduced predator present on the island and were controlled to very low numbers prior to the translocation, comparable to kōkako sites in the North Island. However, since the kōkako were translocated we have become aware that when stoat populations boom on the mainland because of the abundance of rodents during a beech mast, a small number of juvenile stoats leave the mainland and swim the distance to Secretary Island despite it being nearly a kilometre of sea.

Miss Willans said, "We don't have direct evidence to link stoats to the loss of this small founding population of kōkako as they were only monitored with transmitters for nine months following their release, prior to the spike in stoat numbers. It is highly likely, however, that the small spike in stoat numbers on the island may have resulted in the failure of this population to establish. One kōkako was taken by a falcon shortly after its release. Analysis of these threats to a small founding population will be the focus of research and development before any further attempts to translocate kōkako to Secretary Island."

As conservationists continue pushing the boundaries to improve the stakes for native species, they do experience setbacks, but these setbacks frame the new challenges for growing conservation. Mr Steffens said, "Despite this setback Fiordland Lobster continues to actively support the enhancement and protection of our Fiordland marine and terrestrial heritage, and hope that someday the sound of kōkako will be again heard in the Fiords."


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