Five protected birds placed on Parliament's steps by anti-1080 protesters were killed with blunt force trauma, preliminary findings have determined.
Speaker Trevor Mallard has laid a complaint with Police and the Department of Conservation (DoC).
Mr Mallard said the "expert advice was the birds were almost certainly bludgeoned to death."
He said Massey University would be conducting more thorough checks, and that the checks should be able to determine whether the kereru had been killed by window-strike.
All of the dead birds are protected species - two kereru, two weka and one red-billed gull.
The protesters yesterday claimed the birds had been killed with 1080, the poison used by DoC to control pests across New Zealand.
Mr Mallard said he found it particularly "regrettable" that a group of young four or five young children had been used to place the birds on Parliament's steps.