Hidden tribe of kiwi grows from stoat cull

A "lost tribe" of undiscovered kiwi has been found thriving in isolated bush by volunteers trapping stoats at the northern tip of the Ruahine Range, near Taihape.

A group of 29 previously undetected North Island brown kiwi were heard "singing, screeching and growling" among the red beech and red cedar on a perfectly still, quiet evening last month.

Four years ago, Conservation Department staff found only four kiwi in the area.

The latest group is the southernmost population of North Island brown kiwi, and the last remaining group in the Ruahines.

The whio, or blue duck, population has also soared in the area to around 80 male and female birds.

A joint programme by the Conservation Department and Taihape-based Awarua Aorangi Trust targeted stoats in the Ruahine Corner, east of Taihape. In four years, volunteers set 560 traps along 56 kilometres in a control area of between 6000 and 10,000 hectares, killing 210 stoats, 444 rats and 10 weasels.

Conservation Department nest predator control officer Darren Peters said the kiwi – 16 males and 13 females – had been identified by volunteers at 13 selected listening posts hidden in the bush.

The calls were double-checked the following night by experienced kiwi call listeners. The male bird had a "high-pitched whistle", and the female "a screechy growl".

Actual numbers would be higher than those identified by the calls, Mr Peters said.

"They don't tend to sing until they are three years so we don't know how many chicks there were.

"Our methodology is pretty conservative, and we deliberately underestimate the numbers by 20 per cent. We think there may be up to 40 kiwi in the area.

"It's a huge number and a great result from four years ago. It proves that, once you get on top of the stoats, things move pretty quickly."

Kiwi numbers in the area could increase by a third by 2011, he said.

"Nationally, the kiwi population is in decline and there are very few areas now where they survive without control work being done.

"Their best chance is in small pockets like the Ruahine Corner, which we can control."

Chicks weighing between 200 and 300 grams were easy prey for stoats.

"Once kiwis grow to adult size of two to three kilograms they are able to protect themselves."

- © Fairfax NZ News