Predator control brings kākā sex parity

Date:  20 November 2023

Stoats and possums are the key threat to this large forest parrot, with females and chicks the prime targets during nesting when they stay in tree cavities for long periods. Over time, this leads to a male-skewed and declining population.

Surveys for kākā in the Eglinton over the past few years show a thriving population with good numbers of female and juvenile birds, says Department of Conservation Science Advisor Terry Greene.

“The large numbers of kākā we’ve seen and caught in the Eglinton since 2019 clearly show the population is healthy.

“This is a direct result of the long-term predator control, as well as several good breeding seasons following beech seeding events in 2019 and 2023, providing plentiful food.

“It’s really pleasing to see the increase in female kākā, which are now close to parity with males.”

Kākā are often heard but are hard to observe high in the forest. They are surveyed by catching a sample of birds and measuring their beak length, which indicates their sex (males have larger beaks).

During surveys in 2019, 2021 and 2023 a total of 105 kākā were caught, more than 30% of which were juveniles.

Overall, the ratio of females to males was 1:1.3 (43% female and 57% male). In areas without predator control males have outnumbered females as much as five to one.

There have also been lots of comments from tourists about seeing kākā in the area, Terry says.

The Eglinton is one of the most accessible valleys in Fiordland National Park with State Highway 94 to Milford Sound running most of its length.

While they are capable flyers, kākā tend to stay in an area of about 50 ha, although they will move to follow seasonal food sources such as the flowering of tree fushia at The Divide near the head of the Hollyford valley.

There are other strongholds for South Island kākā in areas with sustained predator control including Waitutu Forest in Fiordland, South Westland and Kahurangi as well as stoat and possum-free Fiordland islands.

DOC has been undertaking large-scale predator control in the Eglinton valley for the past 30 years. This includes extensive trapping, use of ground-based toxins and aerial 1080 operations when rodent numbers spike after beech mast (seeding) events (most recently last summer).

Predator control is also benefiting other native species such as long-tailed and short-tailed bats/pekapeka, mohua/yellowhead and tuke/rockwren.

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