Predator control for kiwi survival informs kea research

Date:  15 July 2020

Approximately 40,000 ha of public conservation land in the remote Wet Jacket peninsula area of Fiordland National Park was included in the DOC’s Tiakina Ngā Manu predator control operation last month.

DOC Operations Director southern South Island Aaron Fleming says the primary purpose of this operation was to protect vulnerable kiwi chicks which have been suffering from heavy stoat predation. “Through the Save Our Iconic Kiwi programme, we’ve been monitoring kiwi chick survival at Shy Lake, in the northern peninsula, for the past three breeding seasons and every year it’s the same story. Chicks are hatching, but not making it to adulthood.

“In almost every case – 30 out of 34 monitored chicks – they’ve been confirmed or suspected to be killed by stoats. Last year, the longest-lived chick only made it to seven weeks old.”

Based on that data, the future for kiwi at that site was looking increasingly grim, Aaron says.

“We know the adult population is relatively stable – an adult kiwi is a pretty solid match against a stoat. Chicks on the other hand are extremely vulnerable and if we can’t get a healthy number of them making it through to adulthood to contribute to the population, then we are faced with the reality of one day losing them here forever.”

Wet Jacket, in the heart of the Te Wahipounamu World Heritage Area has never had any type of predator control in the past. Because of this, it’s proving to be a valuable site for further research on outcomes from predator control. Additionally, it’s also providing some data to go towards DOC’s kea management and kea Code of Practice for aerial 1080 operations.

Nationally, DOC is working with Ngāi Tahu and stakeholders on how to improve and build upon years of research into a strategic approach to kea recovery that encompasses the risks and benefits to kea from 1080 predator control, to inform our Code of Practice and other risk mitigation measures. 

“At Wet Jacket, we have been monitoring 21 kea since 2019 in the lead up to this operation. However, prior to the predator control operation, only six transmitters were still active. This could be due to predation – ground nesting kea are very vulnerable to stoat predation, or some transmitters may have fallen off or malfunctioned.”

Sadly, following the operation three kea were found dead. Toxicology reports confirmed the cause was 1080.

“The loss of any kea is always upsetting. At a population level, we know kea do better with 1080 predator control than without it. Following a beech mast, when we get stoat plagues, nesting success in places without 1080 predator control is only about 10%. In places with 1080 operations it’s much higher – about 70%.

“However, it doesn’t make it any easier on the team when we do lose individuals, despite the bigger picture.”

While the sample size of six tagged kea through the operation is not big enough to be representative of the population in the area – and it was never intended to do so – it will still provide valuable insights for long-term management and refining our predator control operations.

Aaron Fleming says DOC’s current focus is around threat mitigation and adaptive management for kea, but will also use these findings for further research into understanding kea behaviour too.

Ultimately, we want to protect as many birds as possible during an aerial 1080 operation, Aaron says.

“Kea conservation is extraordinarily complex.”

“You’ve got these gregarious, intelligent, curious parrots who will take off with anything that isn’t nailed down, and sometimes even nails are no match for them.

“They tamper and get caught in traps, get lead poisoning from eating nails and flashings off buildings, and play in traffic in high-visitation sites. But the number one risk for them is predation from stoats so we need to everything we can to strike that balance between protection at a population and individual level.”

DOC continues to invest significantly to improve our strategy for kea risks from human-led activities, and the results from Wet Jacket will help inform our ongoing approach.

In the meantime, rodent and stoat tracking results from the Wet Jacket operation are expected in August/September, while kiwi chick numbers will be available early next year following this year’s breeding season.  

“1080 remains our best chance to protect these tokoeka chicks – along with many other vulnerable species in the area. A population turnaround won’t happen overnight, but this is a first step into securing their future in Fiordland.”          

Background

Read our blog on why we need to be predator free by PF2050 Programme Manager, Brent Beven.

Shy Lake kiwi study

DOC has monitored Fiordland tokoeka kiwi at Shy lake since 2017 through the Save Our Iconic Kiwi programme. Unmanaged kiwi populations around the country are declining at about 2% per year. The goal for the programme is to turn that around, so every type of kiwi is increasing by 2% per year.

Aerial 1080 used every few years has been shown to increase kiwi populations at places such as Tongariro in the North Island.

There is no direct risk to kiwi from 1080. More than 600 kiwi have been monitored through 1080 operations around the country using radio transmitters and none has ever been found to have been killed by 1080, neither is there any evidence that they eat the baits.

At Shy Lake, which has never received any predator control in the past, we’re comparing chick survival rates in years with aerial 1080 and without. So far, without 1080, we haven’t seen a single chick make it to adulthood.

None of the monitored Shy Lake kiwi have died following this operation. We expect to have the stoat and rodent monitoring results in August/September.

Kea and 1080

Kea (Nestor notabilis) are endemic to the South Island and has a threat classification of nationally endangered. There are approximately 3,000-7,000 birds left and evidence suggests that populations are on the decline and will continue to do so without predator control. 

The DOC ‘Aerial 1080 in kea habitat Code of Practice, 2020’ aims to reduce risks to kea from aerial 1080. We’re continuously working to improve our knowledge and research on risks to deliver the best outcomes for kea and other vulnerable native species.

Kea that live near townships and other human-influenced areas have an increased risk of eating 1080 due to learned scrounging behaviour.

At remote sites, where kea have not learnt to scrounge, they remain innately cautious to novel foods, which lessens their risk of poisoning. Although this it doesn’t mean no risk, as some kea may tamper with bait to their detriment. Research shows the risk to kea lessens with subsequent 1080 operations. This is thought to be due to the favoured survival of kea that are innately cautious -- i.e. selection for neophobic behaviours.

DOC’s published research on kea survival through aerial 1080 operations used results from 222 monitoring cases involving 205 individual kea. These birds were tracked through 19 aerial 1080 operations at 12 South Island sites between 2008 and 2016 to model kea survival. Overall, there were 24 kea deaths all within six of the 19 aerial 1080 operations and only three deaths out of 110 monitored kea at remote sites.

Read DOC's code of practice (PDF, 1430K) for applying 1080 to sites with kea habitat.

Read the toxicology report

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