'He's very protective of the rock': Eagle thinks a rock is an egg

ST. LOUIS (CNN) -- No wonder Murphy the eagle looks like he's sitting on a secret. He is. Instead of incubating an egg, Murphy's incubating a rock. 

"He's very protective of the rock," said Dawn Griffard, the World Bird Sanctuary's CEO.

He squawks when another eagle lands on a branch above the nest Murphy built on the ground. He was injured as a chick and can't fly, which is why he's at the World Bird Sanctuary outside st. Louis, Missouri.

"He just seems very content with this rock," Griffard said.

A keeper shot video after first noticing Murphy acting unusually guarded about a rock in the middle of a nest. Normally eagle parents turn their eggs every few hours, and Murphy can be seen nudging his rock. He settles down to keep it warm. It takes about 35 days for an eagle egg to hatch.

"Will he be sitting there for like a month?" CNN's Jeanne Moos asked.

"Possibly, he might sit there a little longer just to, you know, because it hasn't hatched," Griffard said.

People are smitten with Murphy's dad skills but feel bad that he's incubating a dud. Someone proposed naming the rock "Dwayne the Rock" after you know who.

Another suggested the sanctuary swap the rock with a chick.

"For what reason? He's very attached to his rock," Griffard said.  

A fertilized eagle egg would be hard to come by. And if they slipped in, say, a goose egg, who knows how Murphy might react. The sanctuary CEO says birds whose eggs don't hatch properly tend not to show signs of being depressed. So when you joke, "who's going to tell him?" Griffard said, "I don't think anybody has to tell him. I think he'll figure it out."

Humans went through a pet rock phase. Why can't Murphy?

If you want to see eagles with real chicks (no offense to Murphy) you can watch the Hays eagle nest on KDKA.com 24/7.