The number of wedge-tailed eagles dying after coming into contact with electricity network infrastructure is up by more than 140 per cent from the last year, TasNetworks' annual report reveals.

Key points: 29 wedge-tailed eagles were killed by power lines in 2017-18

29 wedge-tailed eagles were killed by power lines in 2017-18 The adult population in Tasmania is estimated to be about 700

The adult population in Tasmania is estimated to be about 700 The death rate warrants listing the eagle as endangered, expert says

Twenty-nine wedge-tailed eagles were killed in 2017-18 — a dramatic rise form from the 12 killed the previous year.

This was despite TasNetwork's pledge last year to invest $600,000 to install infrastructure that would reduce the impact on the threatened birds.

Tasmanian wedge-tailed eagles are classified as endangered, with the adult population estimated at about 350 breeding pairs.

A grey goshawk and a white-bellied sea eagle were also killed in the past financial year.

BirdLife Tasmania convenor Eric Woehler described the deaths as a "terrible loss" for the wedge-tail population.

"To lose 29 birds in one year is a significant number of birds, and it's a significant hit on the population in Tasmania," he said.

"They're a long-lived bird, they can live for 30 or more years. To lose this many birds is going to take a long time — if ever — for the population to recover.

"The population is decreasing at such a rate that it meets the international criteria for listing as an endangered species.

"If we don't stop the threats that have been identified … the species will go extinct."

'Eagle deaths in previous years possibly underestimated'

Mr Woehler questioned why the deaths had increased by so much compared with previous years.

He said if the increase was due to better reporting, it was likely numbers had been underestimated in previous years.

Eleven wedge-tailed eagles deaths were reported in 2015-16.

TasNetworks chief executive Lance Balcombe described the spike as "unfortunate", and said his organisation was working with scientists to develop an eagle risk strike model and to fit mitigation devices to parts of the network where bird strikes occur.

He said TasNetworks had been focusing on reporting eagle injuries and mortalities, and would spend up to an additional $2 million this year in an effort to address the issue.

"We got the message out to the community — farmers, in particular — that we want to hear about eagle mortalities because with that data, although it's a bad outcome where a bird is killed, the good thing is we can do something with that data," he said.

"We can go and mitigate that part of the network, and the more data we have, that will go and help the science that we're trying to develop."

TasNetworks also reported three incidents related to the wrongful disconnection of registered life support customers.