A wildlife expert has called for independent monitoring and studies into eagle deaths caused by windfarms, warning the problem is only going to get worse as the industry expands in Tasmania.

Key points: Twelve eagle deaths have been reported by Tasmania's largest wind farm since its construction in 2013

Twelve eagle deaths have been reported by Tasmania's largest wind farm since its construction in 2013 Under the law, windfarms must pay offsets when such endangered birds are killed

Under the law, windfarms must pay offsets when such endangered birds are killed A wildlife expert has criticised the system, saying the actual death rate could be higher than reported and that the offsets are 'blood money' that are ineffective

Under Commonwealth legislation, windfarm companies agree to "offsets" when an endangered bird is killed.

Offsets include the companies paying compensation, funding research or the protection of nest sites.

"A lot of people call it blood money — it's compensation for killing endangered species," wildlife biologist Nick Mooney told Leon Compton on ABC Radio Hobart.

Sorry, this audio has expired No evidence popular wind farm offset protects wedge-tailed eagles: Nick Mooney

Musselroe Wind Farm, Tasmania's largest, has reported 11 wedge-tail eagle deaths and one white-bellied sea eagle death since it was constructed in 2013.

Mr Mooney believes the mortality rate is higher.

"We don't know how many are killed, there is no proper study," he said.

It is estimated there are less than 350 breeding pairs of the endangered Tasmanian wedge-tail eagles, and in 2017–18, 29 were killed by powerlines.

Mr Mooney has raised concerns with how offsets are decided and set, and said they are based on modelling and projections rather than real data.

"It's almost a nonsense to be setting offsets on speculation," he said.

"We're building all these windfarms without knowing the damage we're doing."

There's thought to be less than 350 breeding pairs of Tasmanian wedge-tail eagles left. ( ABC Hobart: Georgie Burgess )

'Offsets not working'

The Musselroe Windfarm, owned by Woolnorth, offsets deaths through funding the protection of wedge-tail eagle nests on private land.

"The trouble is, the assumption is that will increase production of eagle chicks to compensate for deaths," Mr Mooney said.

"But you need about 12 extra eagle chicks to compensate for every adult eagle killed at a windfarm.

"There's no evidence the covenanting process has increased production at all."

A spokeswoman for Woolnorth said protecting eagles was "extremely important" to the company.

"There are very few eagle collisions at our wind farms and they in no way threaten the bird's sustainability," she said.

"Woolnorth is trialling a number of mitigation projects and will continue to offset eagle impacts that occur at its wind farms, in addition to continuing to work with state and Commonwealth regulators to manage the impact on eagles."

There were no eagle deaths reported at its Studland Bluff and Bluff Point windfarms between 2016 and 2018.

Mr Mooney says an independent study is needed into how many eagles are being killed by turbines. ( Flickr: Jim Bendon )

Potential conflict of interest

Mr Mooney said while there is no suggestion companies are hiding bird deaths, the system of reporting was a potential conflict of interest.

"The amount of offsets you pay is related to the number of eagles you're found to be killing," he said.

He said searches for dead or injured birds were often underneath and near turbines, meaning some may not be found and reported.

"Anything with wings is going to wobble off."

Mr Mooney said real data needed to be collected, and a proper study of eagle populations around windfarms was needed.

"It's inexcusable not to have eagles with GPS packages on them to find out how many were killed," he said.

The Cattle Hill Windfarm, which is still under construction, has committed to trailing new technology to prevent eagles being kill in turbines.

It will install monitoring towers to identify when an eagle is in the flight path of a turbine and shut it down.

A spokesperson for the Environment Department said the Environment Protection and Biodiversity Conservation Act set out the requirements for offset proposals and used the most recent available scientific literature.