Autopsies of the birds laid on the steps of Parliament during an anti-1080 protest in September show none died from the poison and one protected species had been shot.
Six birds - including kererū, weka, red-billed gull and kingfisher - were strewn across Parliament's steps, in what activists labelled "an act of theatre."
Parliament's speaker Trevor Mallard said at the time that the birds appeared to have been bludgeoned and laid a police complaint.
Autopsy results show two of the birds were hit by vehicles, two flew into windows, one was too decomposed to tell the cause of death and an adult Weka appears to have been shot, most likely with a .22 rifle.
Forest and Bird said the protest leader needed to tell police who killed the protected bird.
"Weka are such special birds, anyone who encountered one will have a story to tell. It's very concerning that someone out there has deliberately hurt a native bird, and passed it on to be used as a prop in their campaign of misinformation," said chief executive Kevin Hague.
"Like all our native animals, weka need their forest homes to be from safe rats and stoats. We should all be supporting the Department of Conservation (DOC) to do what they do best, which is care for our native wildlife.
"It's an offence under the Wildlife Act to shoot protected birds. The protest leader mislead the country by claiming the birds had been killed by 1080, and then denied he said it. He needs to distance himself from this latest criminal act and tell the police what he knows about who killed this weka," Mr Hague said.
However, it's unlikely anyone will be charged over the shooting of the protected bird.
Police and Parliamentry Service have handed the results of their investigations to the Department of Conservation.
DOC said it spoke to one of the protestors, but it hadn't been able to establish how or when the weka was shot.
"Whilst acknowledging the fact that one of the birds was shot is concerning, the task of establishing to the evidential standard required, who, how and when this weka was shot has proven too difficult," Alan Christie, the department's principal compliance officer said.
Despite this, it said the investigation was ongoing.