Sibling rivalry has nearly claimed the life of an osprey chick which belonged to a family of endangered raptors that has attracted a cult following online.

For three years, a camera has been monitoring a nest of eastern ospreys on a pontoon near the coastal city of Port Lincoln in South Australia.

But tensions boiled over on Wednesday, when a larger, more dominant chick managed to eject its smaller sibling - prompting an urgent rescue by an anxious group of people, who watched the drama unfold on a live video feed.

"We jumped in a dinghy, went out there and picked up the chick - it was very, very weak and floundering in the water," Janet Forster from the Port Lincoln Ospreys Facebook page said.

"Once it was thrown into the water, it was going to die, so at least it's been saved now."

Stevie, the rescued osprey chick, is examined by a Port Lincoln vet. ( Supplied: Calypso Star Charters )

Ms Forster's company, Calypso Star Charters, has spent thousands of dollars monitoring the nest for about seven years.

She said the brutality of nature was especially pronounced for this year's hatchlings, who she guessed were days from leaving the nest and starting their own lives.

"The oldest chick is very dominant, and [last Sunday] it really attacked the young one - we thought it had killed the chick," Ms Forster said.

"But it hadn't, it still survived, and that night they were all fine.

"On Wednesday morning, they were both lying side by side, there was no food, and the eldest chick just got up, landed on top of the younger one, and really struggled with it until it kicked it over the nest and into the water."

The rescued osprey - which has been named Stevie after wildlife warrior Steve Irwin - was taken to the vet and given the all clear.

It has now been flown to its new home at Kangaroo Island's Raptor Domain with the blessing of South Australia's Environment Department.

Eastern ospreys are found along much of Australia's coastline and can have a wingspan of up to 170 centimetres.

"On the screen it doesn't look that big, but it is a big bird," Ms Forster said.

"It's just a great timewaster, I've got to tell you, I could spend all day watching these birds."

In happier times, Stevie the osprey chick enjoys a meal while its sibling and mother watch on. ( Supplied: Calypso Star Charters )

Port Lincoln proclaims itself as Australia's seafood capital, but Ms Forster said the ospreys had become local celebrities.

"They leave the nest, fly over the Port Lincoln Marina, and it's surrounded by houses," she said.

"[The male osprey] sits on the light pole on the bridge, looks at the fish, and dives down and catches them - a lot of the local photographers are over there waiting to see when he comes in.

"It's really good for the people in the town that are interested in birds to be able to see them like they do."

In 2005, it was estimated there were as few as 52 breeding pairs of eastern ospreys in South Australia, but numbers nationally are thought to have increased in that state and New South Wales.