Tīeke population 'severely impacted' by stoats at pest-free Auckland regional park

Friday, 14 May 2021

A stoat is captured by a thermal camera designed to monitor pests at Auckland's Shakespear Regional Park.

Rangers fear stoats at Shakespear Regional Park may have had a severe impact on the pest-free sanctuary’s tīeke population.

The park, on Auckland’s Whangaparāoa Peninsula, is a sanctuary that provides wildlife, such as little spotted kiwi, robins, whiteheads, and hihi (stitchbird), with a safe and pest-free habitat.

A 1.7 kilometre pest-proof fence was built between Army Bay and Okoromai Bay in 2011 and a pest eradication programme implemented to monitor the 500-hectare sanctuary.

However, a stoat was detected in the sanctuary at the end of 2020. That prompted Auckland Council to rent, and later purchase for $4000, a thermal camera from 2040, a not-for-profit that develops equipment to monitor bird and predator populations alongside the Cacophony Project.

A survey of the sanctuary was expected to find 100 tīeke (North Island saddleback), however only 30 were found. (File photo)

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Shakespear Regional Park, sitting at the end of the Whangaparāoa peninsula, is New Zealand's most visible and accessible open sanctuary.

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That stoat later gave birth, and two of its kits – a male and a female – were caught in traps.

Then, in January, thermal camera imaging suggested there were still stoats in the sanctuary, including the mother.

Stoats pose a significant risk to threatened native birds and lizards – with one believed to have killed three tūturuatu (shore plover), one of the world’s rarest shorebirds, on Motutapu Island in January.

Stoats are 'public enemy number one' for New Zealand birds, the Department of Conservation says. (File photo)

On Thursday, the council’s senior ranger at the sanctuary, Matt Maitland, said three more stoats had been captured, including two males and a female.

He believed one more stoat remained at large.

The sanctuary’s tīeke (North Island saddleback) population has been “severely impacted” by the stoat outbreak, Maitland said.

“This is the most significant excursion to date.”

The tīeke was once widespread across the North Island. However, the population was decimated by introduced predators in the late 1800s.

In the 1960s, the Department of Conservation, known as The New Zealand Wildlife Service at the time, saved the species from extinction by translocating it to different islands in the Hauraki Gulf.

The species now thrives on 19 islands and is in a favourable position to survive, according to the DOC website.

In 2018, 50 tīeke were released into the sanctuary.

A survey by volunteers in March was expected to find about 100 birds, however only 30 were found.

“Earlier investigations within the sanctuary have revealed a number of sites where stoats keep birds they have killed to consume later. The sites included dead kererū, tūī and bellbirds.”

Maitland feared there could be more bird deaths, given they were stoats’ main food source.

The capture of the male stoats would hopefully thwart any further breeding, Maitland said, however the remaining stoat would need to be captured to make sure of that.

“Stoats were previously eradicated, and we want to return the open sanctuary to being stoat free as soon as possible so that our native species can continue to thrive there,” Maitland said in April.