A remote controlled plane was caught in what seemed to be an attack on a juvenile sea eagle in the Don River area on Sunday.
Ulverstone photographer Tony Roberston was out with his camera hoping to see them when he saw one of the raptors flying up with a small plane under it.
"We were out there about 3pm.
"One bird flew out over the river and we were taking pix of it, then one flew up to greet it and then we thought it was three birds, but when we used the lens we realised it was a plane."
He took a few shots of the plane heading towards the eagle, then kept his eye on the birds.
"They flew near us and we kept looking at them so I imagine the plane returned to its owner."
Mr Roberston did not want to give out any hint of the birds' nesting site for fear of people going there to harass them.
"A walker going past thought he recognised the plane, and said he might know who owns it; that only recently that guy had been complaining that eagles are smashing up all his drones and planes," the social media post said.
"It's possible we have someone regularly targeting the eagles, and with a drone, nowhere would be safe," the post stated.
Mr Robertson said he had contacted the wildlife compliance officer at the Department for Primary Industries, Parks, Wildlife and Environment.
"I'm just trying to get public awareness that someone's been doing this," he said.
"I do bird photography and I love raptors."
Bird of prey expert Nick Mooney said if anyone chased the sea eagles or attacked them with a drone or remote controlled plane, that was an offence.
"Shooting at them, catching them or attempting to catch them is an offence. The birds are protected. This person could be committing an offence and they could be fined thousands of dollars."
Mr Mooney, who also heads the raptor group for BirdLife Australia, said he'd never heard of such a thing before.
"This is the first time I've heard of someone harassing the birds (with a drone).
"We've had birds of prey crippled by them before. The propellors can cut their feathers.
"You can fly drones and if the birds have a go at them that's not your fault. But you can still panic them and make them fly into power lines or they might grab the drone and injure themselves."
DPIPWE regulatory services manager Andrew Crane said he could confirm the department was investigating the incident and was calling for information from the public.
"The deliberate use of a drone or model plane to chase or attack an eagle could have fatal consequences for the bird of prey.
"There is plenty of evidence to show that eagles species will interact with drones or model planes and are likely to be injured, often fatally," Mr Crane said.
"Eagles are territorial and will defend their territory from threats, but they can also be easily spooked by model aircraft as well."
Tasmania's threatened species legislation was amended in 2018 after several incidents involving the deliberate killing of eagles. Changes included raising the maximum penalty to more than $100,000 and/or one year in jail.
"Based on eyewitness accounts this would appear to be a clear case of someone using a model plane to chase a young White-bellied sea-eagle, potentially severely injuring or killing that bird.
"This is a serious offence and we would welcome anyone with more information to come forward. Information can be provided anonymously either to our hotline on 0417661234 or to Crime Stoppers on 1800 333 000," Mr Crane said.