“Murphy is not hurt, sick, or otherwise in distress,” the sign read. “He has built a nest on the ground, and is very carefully incubating a rock. We wish him the best of luck!”

A tweet about Murphy’s mission quickly went viral, leading thousands to follow along as he tried to hatch the rock, though they knew it was impossible. Then, in a twist, Murphy’s new fans got to see the eagle become a father after all when, in early April, he began to bond with an eaglet the sanctuary received.

“He was sitting on a rock and everybody told him, ‘It’s a rock, it’s not going to hatch,’” said Dawn Griffard, CEO of World Bird Sanctuary. “And all of a sudden, in his mind, it hatched and he has a chick.”

Murphy first arrived at the sanctuary, which tries to release the birds it receives back into the wild, about 30 years ago.

He was transported from Oklahoma with a broken leg that was treated at World Bird Sanctuary before he was released. But he soon returned with a broken wing.

Staff determined he had suffered permanent damage that made him unable to fly or survive in the wild, where most eagles live 20 to 30 years, and he has lived at the sanctuary ever since.

Murphy was in the center’s bald eagle aviary with four others in early March when staff first noticed that he’d taken to one of the rocks in the enclosure.

Over several weeks, Murphy had become so protective of his rock that he wouldn’t allow the other four eagles near his side of the enclosure, Griffard said. If they tried to come anywhere close, he screamed or charged at them.

While Murphy had not incubated like that before, Griffard said it’s not uncommon for birds during the spring breeding season when their hormones run high. Some try to incubate rocks or golf balls when they don’t have their own offspring, she said.

“We’ve never had a bird at the sanctuary protect a nest like that, so viciously,” Griffard said. “He was very much about it.”

A few days after Murphy had started to protect his “rock baby” too aggressively, on April 4, the sanctuary staff moved him to a separate, private enclosure, she said. Little did Murphy know that soon he’d have a real chick under his wings.

That same week, rescuers brought a baby eaglet to the sanctuary from Ste. Genevieve, Mo., following a windstorm that had blown its nest down. The other eaglet it had shared the nest with died in the fall, Griffard said.

After the eaglet was checked for injuries, the sanctuary staff’s next task was to figure out which eagle to bond it with. They wanted to avoid any imprints with humans, as that would prevent it from being released back into the wild.

Griffard said Murphy was “the best choice.”

“He was already showing the hormonal aspects of raising a chick,” she said. “And he was taking such good care of his rock that we decided that he would be our best bet.”

But Murphy only had experience caring for a rock. So sanctuary staff decided to place the eaglet in a small cage they then put inside Murphy’s nest. They monitored the bonding process carefully through a camera in the enclosure. The eaglet was released from its cage on April 13, after about a week in the nest with Murphy.

That was when Murphy “really showed interest,” Griffard said.

That morning, Murphy was given a full fish, and the eaglet had small chunks placed in the nest to eat. When keepers checked to make sure both had eaten, Murphy’s fish had been torn apart, but the eaglet’s pile of fish was untouched.

However, the eaglet’s crop, an area under its chin where food is stored, was full — meaning Murphy had fed his chick.

As Griffard and the World Bird Sanctuary posted updates online, heartwarming comments came pouring in from supporters across the country.

“People are saying he’s not the stepdad, he’s the dad that stepped up,” Griffard said.

Soon, staff will begin training the eaglet to fly and to hunt, preparing the chick to be released back into the wild this summer.

But, Griffard said, people shouldn’t worry too much about Murphy being sad or lonely when that happens.

“There is a point where eagle parents know that it’s time for the chick to leave,” she said. “And they almost kick the chick out of the nest. So, he’ll know.”