An autopsy of the dead birds dumped at Parliament by 1080 protesters in September shows that one was shot, likely with a rifle.
The cause of death of the adult male weka is ruled to be "trauma consistent with ballistic injury".
"Entry wound would indicate a ballistic calibre of .22 should be considered."
Weka are a protected species.
Under the Wildlife Act, it is a crime to shoot a protected species.
Forest and Bird is calling for the 1080 protesters who dumped the birds on the steps of Parliament to tell the truth about how the bird died.
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"It's very concerning that someone has deliberately hurt a native bird, and passed it on to be used as a prop in their campaign of misinformation," says Forest and Bird's Chief Executive Kevin Hague.
"The protest leader misled the country by claiming the birds had been killed by 1080, then denying he said it. He needs to distance himself from this criminal act and tell the police what he knows about who killed this protected bird."
Of the results released, two birds had flown into a window, two had been hit by a car and one was too decomposed to tell the cause of death.
Newshub approached Alan Gurden, the co-organiser of the Poisoned Nation hikoi protest for comment, but he could not be reached at this time.