An endangered population of kaka in the Waitutu Forest, Fiordland, has been boosted by a record breeding season following a pest control operation with 1080 toxin.
In October 2010, the Department of Conservation (DOC) carried out an aerial possum control operation over 25,000 hectares of Waitutu Forest using cereal pellet baits laced with biodegradable 1080.
Field teams have made several monitoring trips into the area since the 1080 operation and found that possum, rat and stoat numbers have plummeted. In addition, female kaka radio-tracked prior to the operation are all thriving – with nests full of healthy chicks.
“This is great news for the forest and its birdlife” said Colin Bishop, DOC’s Murihiku Area Ranger - Biodiversity Threats. “Species that were heading for extinction within this forest now have a good chance of survival.”
Kaka, once abundant in the forest, have been decimated by predators. So many nesting female kaka had been killed that they were deemed to be heading for extinction when surveyed six years ago.
“They were in desperate trouble – it looked like curtains for our perky forest parrot. We helped them along four years ago with trapping in a small area of the forest, but now this 1080 operation means we’ve covered a huge area and given more birds more of a chance,” said Mr Bishop.
“Already this year we’re seeing the best fledging success for decades – more chicks are surviving until they’re old enough to look after themselves. That means more females, more chicks down the line, and a real chance to get our kaka back from the brink.”
While possums were the primary target of the poison operation, high kills of rodents and stoats also achieved another positive spin-off. Possum numbers have been reduced by 99.5% within the treatment area and the number of rodents and stoats have been reduced to a level where they are not detectable with standard monitoring methods.
Southland Conservation Board Chairman Robin McNeill said: “Aerial 1080 is our last real chance to save Waitutu. Believe me – possums, rats and stoats have made Fiordland a green desert. Good science must prevail to save a precious oasis for us all to enjoy.”
Local birdlife was monitored both before and after the operation including, tomtits, grey warblers, rifleman, mohua, kaka and ruru. No birds were found to have been killed by the poison, including 15 kaka and 11 ruru/morepork which were monitored. There was no detectable reduction in bird numbers as a result of the operation, and it is clearly evident that bird numbers are now on the increase due to the reduction in predators.
“Using 1080 allows birds to breed and their chicks to survive. It also allows forest canopies to recover from damage caused by possum browsing” said Mr Bishop. “The future is now looking better for Waitutu.”
Water samples were also tested from 12 sites in the area and no traces of 1080 were detected. The total cost of the aerial control was $23.65/ha compared to recent ground control in this area which cost $40.62/ha.