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Chatham Island taiko (Magenta petrel) Pterodroma magentae  Photo Crown Copyright © Department of Conservation

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The miraculous Chatham Island taiko rediscovery and comeback from the brink of extinction

The Chatham Island taiko was declared extinct, but was rediscovered by David Crocket in 1978 at the south-east corner of Chatham Island, 111 years after it was first found at sea.

It took nearly a decade before the first three burrows were found in 1987 with the aid of radio transmitters.  By 1999, more than two decades after the taiko was rediscoverd, a total of 23 burrows had been found.

The population was still in decline and on the brink of extinction in 1994, when just four breeding pairs were known, although it was possible that others remained undetected. 

Chatham Island taiko have made a slow comeback in the decade since their low point, with a known population of 120 birds, including 15 breeding pairs in 2004.

It is estimated that taiko went through a massive decline of 80 percent over 45 years.  The predominence of taiko bones in Moriori and Maori middens indicate that it was extensively hunted for food.

Introduced pigs, cats, dogs and rats have been principal predators of taiko.  Native buff weka introduced from Otago in the South Island where they are are now extinct, also prey on eggs and chicks, and compete for their nesting burrows.

Because the Chatham Island taiko's breeding habitat is in native forest, 4 to 6 kilometres inland, clearing for pasture has been another factor in the decline.

The Chatham Islands are at the eastern perimeter of the Chatham Rise, an undersea plateau which is the most intensive New Zealand commercial fishery.  Many petrel have been killed, and while the species of bycatch have not been documented, it is reasonable to assume that many taiko and Chatham petrel have been fatal victims of fishing.

During six-weeks of fishing for ling in 2001 on the Chatham Rise, 293 petrels and 11 albatross were killed by longlines set by one Nelson-based fishing boat.

Breeding was slow to comeback with only 16 fledglings observed between 1987 and 2006. Breeding in 2002 was exceptional when seven chicks were fledged.

There were 35 active burrows, 25 breeding pairs, and 11 known chicks in 2006, which brought the number of chicks fledged up to 63 since 1987.

Critically endangered seabird losing its pulling power

23 April 2008 Birdlife International

A study into one of the world’s rarest seabirds provides knowledge that could help avoid extinction.

Molecular analysis of the critically endangered Chatham Island taiko Pterodroma magentae, also known as the Magenta petrel, discovered that 95 percent of non-breeding adults were male.

This suggests that critically low population levels may be causing male birds difficulty in attracting a mate.

Their calls are too spread out to attract the infrequent females that pass by.

Conservationists plan to increase the male’s pulling power by creating a new breeding colony within a predator-proof fence.

There are now thought to be between 8 and 15 taiko breeding pairs remaining in the world.

Male and female magenta petrels look extremely similar, and are difficult to distinguish by sight alone. Scientists collected blood samples from almost the entire known living population over a 20 year period.  This allowed the team to distinguish gender accurately using DNA sexing techniques.

The sex-ratio of males to females was approximately even in petrel chicks and breeding adults.  However, 95 percent of non-breeding birds were found to be male.  This finding suggests that unpaired males may be having difficulty in attracting females to burrows.

Conservationists are helping to increase the petrel’s density by focusing birds within the Sweetwater Secure Breeding Site.  This is being achieved by translocating chicks, and by using calls to attract adult petrels to the refuge.

Eight chicks were successfully moved and fledged last year, and The Chatham Island Taiko Trust was established in 1998 to provide legal status to the continuing work.

Scientists are hoping to use knowledge of male behaviour traits to make the plan work.  “It has been found in other petrel species – such as Manx shearwater Puffinus puffinus, Cory’s shearwater Calonectris diomedea, and Wandering albatross Diomedea exulans - that males return most frequently to the site where they were reared as a chick”, commented Ben Lascelles BirdLife’s Marine IBA Research Assistant.

By using the DNA sexing technique to slightly favour male chicks for translocation, the team hope to increase the numbers of birds returning as adult breeders to the refuge.