The Department of State Growth covered the hollows of potential swift parrot nesting trees at a proposed Tasman Highway widening near St Helens despite being told to seek advice from the Commonwealth first.
Right to Information documents show the Natural and Cultural Heritage Division in the state's Environment Department advised State Growth that the presence of swift parrot habitat could make it a Commonwealth matter.
They also detail a net loss of foraging habitat until offset trees mature.
"NCH advises that the proponent seeks advice from the Commonwealth in regard to potential impacts on the swift parrot and make themselves aware of their obligations under the EPBC Act," the documents read.
When questioned about the documents in Budget estimates, neither Infrastructure Minister Michael Ferguson nor departmental officials could say whether they had sought advice from the Commonwealth before covering the hollows.
The question was taken on notice.
Local residents spotted hollows covered with boards in September. Six hollows had been covered, despite the works yet to be approved by Break O'Day Council.
Mr Ferguson said the department acted on advice from ecological consultants.
"At a high level, I'm advised that the response is a conventional and sensible one," he said.
"The trees that are listed for removal for the road widening project, the right thing to do is to block the nesting hollows so that when the birds are exploring nesting sites, they will not be able to find one in those trees and they will find a different tree which will actually continue to be appropriate habitat for that.
"It's about saving the destruction of nests, actually."
Greens leader Cassy O'Connor suggested this would diminish habitat, to which Mr Ferguson responded, "maybe that is so".
Ms O'Connor said the logic behind the hollow coverings was "twisted".
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