The deaths of two endangered native parrots from Orokonui Ecosanctuary have been attributed to human error.
Two kākā are believed to have died after ingesting brodifacoum, an anticoagulant meant for possums.
Orokonui conservation manager Elton Smith said Ospri and Predator Free had not undertaken a proper assessment of risk, leading to the preventable deaths.
"kākā have not been taken into consideration when using pest control tools."
The loss of the kākā was a tragedy and an unanticipated risk, Ospri southern South Island programme manager Eric Chagnon said.
The operation was carried out as part of the TBfree programme which aimed to eradicate bovine tuberculosis in possums, he said.
There would likely be national changes to the programme as a result of the incidents at Orokonui, and Ospri would be closely involved in that process - particularly where it knew kākā were present.
Mr Smith said one bird died at Orokonui on about November 1 after showing symptoms of sickness.
"The bird was high up a tree and did not move for five or six hours, which is unusual.
"It began to sway, and the following day the same bird was found dead."
The other bird showed similar symptoms and was found dead at a private property in Osborne, 7km from Orokonui, on Wednesday.
Initial autopsy results suggested brodifacoum was present in the kākā - the same toxin was used in the Ospri operation.
Mr Chagnon said Ospri removed the bait traps to ensure no more kākā would be affected.
"We've responded very quickly which highlights how important it was to us.
Since Thursday, more than a dozen contractors had removed all of the bait from stations across the 12,500ha operation.
"It's going to cost us significant resources and is a setback, but it is something we need to do to make sure we don't affect any more kākā."
Mr Smith said credit should be given to Ospri for its actions after the deaths.
"They did ask us for advice and we told them to take out the bait stations as soon as possible, which they did.
"Unfortunately, there will probably be more than two kākā deaths; time will tell."
A meeting on Thursday between Orokonui Ecosanctuary, The Halo Project, Ospri, Ospri contractors and the Dunedin City Council discussed what steps should be taken by stakeholders.
The livers of the dead kākā would undergo further autopsy to determine what was in the birds' stomachs.
Once the cause of death was confirmed, the next steps would be determined.
In future, Predator Free New Zealand and Ospri needed to consult Orokonui and similar organisations before installing bait stations near areas where crucial wildlife lived, Mr Smith said.
"We've lost at least two breeding female kākā.
"Breeding females are gold - they should have lived for 30 years."
Mr Chagnon said Ospri had been working in the area since 2018 and had eliminated more than 20,000 possums.
"We've been successful in our goal, but in hindsight we definitely would have done things differently such as consulting with outside stakeholders."
DCC parks and recreation group manager Robert West said Ospri had confirmed it had the possum control work and immediately removed all toxins from bait stations on both council and private land in the area.
"We have been pleased with the speed of Ospri's response to this situation, and for the way in which they have kept us informed."
Predator Free Dunedin technical adviser Mike Thorsen said thought needed to be given to preventing further kākā deaths.
"The last thing we want to be doing is making it unsafe for wildlife. It's counter to what we're trying to achieve.
This article was first published in the Otago Daily Times.