Kākā females making a fourfold comeback in the King Country

Wednesday, 29 September 2021

A Kaka was spotted in a tree by the University of Waikato.

The female kākā population has more than quadrupled in the King Country, thanks to a long-term monitoring programme.

Between 2000 and 2007 the population has increased from 600 birds to about 2,600 birds during 2020 – an average annual population increase of 6.4 per cent.

The monitoring programme in Pureora Forest Park follows pest control in Waipapa Ecological Area, tipping the balance back towards a more even sex ratio.

Female kākā sit on the nest for extended periods of time incubating eggs and tending to chicks, but they are easy prey for pests like stoats and possums, resulting in the skewed sex ratio.

Project Janszoon and the Department of Conservation launched a breeding programme for northern South Island kaka in 2017 to improve the genetic diversity of the native parrot being introduced to Abel Tasman National Park.

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Terry Greene, Department of Conservation science advisor, said populations which did not have pest control were highly skewed towards males because females are killed on the nest.

However, with pest management, Pureora has seen the previous 1:2.1 sex ratio (2.1 males for every one female) come back into balance and closer to 1:1.

Kākā are episodic breeders which means their breeding is linked to the availability of food resources. They sync their breeding cycles with mast events where trees produce and drop a significant number of seeds/fruit, providing ample food supplies for the birds.

When there is a lot of food around, they go for it and even breed twice a year if they can, Greene said.

“We believe they live in the order of 40 years in the wild. They have variable numbers of chicks depending on the food crops available.”

But mast seasons can also spell disaster for native birds with an increase in rat numbers.

“Kākā breed the year seed is produced, and the pest populations expand after that.

“Rodents get stuck in, and numbers climb in winter and by spring, they breed and take off. Stoat populations follow behind in October and suddenly seed drops off and stoats start eating more birds.”

North Island kākā are at risk, or recovering; South Island kākā are nationally vulnerable and Chatham Islands kaka are extinct.

DOC has controlled pests within the Waipapa area since 1993 using 1080 every three years and ground bait stations annually.

Te Kuiti based senior biodiversity ranger Jon Sadler said there are more than 2000 bait stations on the ground and the new kākā population results show the work is paying off.

Every October, for a week, annual monitoring of the birds is coordinated.

A grid of about 130 points is laid over the area and DOC rangers, contractors and volunteers go to the points with GPS and stand there for 10 minutes. They use a laser range-finder to measure the distance to the nearest metre and go point to point in pairs to maximise detectability.

It’s the only one of its kind in the country, Greene said.

“We don’t have density and abundance data like this because it’s difficult to resource long-term studies going and people move on. It’s fortunate the people who work in Te Kuiti have maintained it.

Sadler and Greene hoped that kākā become socialised and more common in the remaining mainland forest and the population is maintained in Waipapa.