Rescuers have released a bald eagle after removing a 3.6-kilogram ball of ice from its tail feathers, which left the iconic US bird unable to fly.

Key points: The ice ball was only a few hundred grams lighter than the bird itself

The ice ball was only a few hundred grams lighter than the bird itself Volunteers had to give the eagle a warm bath under a tap to remove the ice

Volunteers had to give the eagle a warm bath under a tap to remove the ice The eagle was released back into the wild after recovering at a rehabilitation clinic

The eagle was spotted on the ice of the partially-frozen Lake Michigan earlier this month following the polar vortex, eating along with three other birds.

But when the trio flew off, the fourth eagle was left hopping along the icy surface alone.

Volunteers from bird welfare group Wings of Wonder were called to the lake in Suttons Bay and eventually corralled the adult male and took him in for treatment.

Mr Scott said the eagle appeared to be happy to be rescued. ( YouTube: Ken Scott )

It was soon discovered the eagle had dozens of icicles on its tail feathers, but the big problem was a large snowball stuck to its rear end.

Rebecca Lessard, the welfare group's director, told the Detroit Free Press the ice ball was only a few hundred grams lighter than the bird itself.

"He just had a bowling ball under him," she said.

The added weight would have made it difficult for the eagle to hunt, meaning he could have starved. The exposure to ice also left him vulnerable to frostbite.

Ken Scott, who filmed the rescue effort, said the eagle seemed to have been looking for help.

The snowball was nearly as heavy as the bird itself. ( YouTube: Ken Scott )

"We set him up overnight in a crate near a heat vent hoping the freezerlings [sic] would let loose, but alas, the big one did not," he said on YouTube.

"The next morning, Jim Manley joined the crew to help with the next step of 'forced defrostation' [sic]... warm tap water directly applied to the ice ball.

"They were able to remove the ice beast and it was apparent he was pretty happy to have his discharge chute operating again as he was making up for lost time... with cleared out piping he gently accepted his first free meal very gently from forceps."

The volunteers cared for the eagle for about a week, feeding him rabbit, rat and fish while monitoring his flying abilities.

Assured he was healthy and able to survive in the wild, volunteers released the bird in front of a crowd of locals.