Because he's a juvenile and still learning to hunt, Peanut will need help. So staff from the center will visit often to leave dead rats, just in case.
Hawks began nesting on a third-floor ledge of the Franklin Institute in 2009.
Lately, the hawk family has seemed as unlucky as it is celebrated, attracting millions of views on live video of their nest and a multitude of hits on their blog ( http://sunnydixie.blogspot.com).
Last year, the adult male was hit and killed by a vehicle on the Schuylkill Expressway. The young were still in the nest, and the female couldn't both feed and protect them.
Against all odds, another male showed up, the female accepted him, and the food drops for the young hawks continued.
Then came this year's tragedies - two birds dying after striking windows, and then Peanut's brush with death.
He was named Peanut because he was the smallest of the three hatchlings, but some still cringe at the notion of a cute name - or any moniker - for such a wild and noble creature.
The bird was found dazed and immobile near the Parkway early July 30, and an alert went out over Facebook - the hawks have a page there, too - that there was a "hawk down."
One of the Hawkaholics, as the birds' fans and watchers call themselves, was nearby. She happened to be a wildlife rehab volunteer with heavy gloves and a box in her car.
X-rays found no fractures, and the rehabbers began to work. First he needed to be hand-fed, then he ate on his own, and then he loudly demanded food.
Finally he began to spend time in a flight cage, testing his wings.
Rick Schubert, director of wildlife rehabilitation at the center, knew the bird was ready to be released when he was "flying from one end to the other, doing 180s in midair."
Also, he was "eating everything in sight."
Marsha Perelman, chair of the Franklin Institute's board, was at the release. Peanut flew immediately to a nearby tree, and "it looked as though he had been there his whole life," she said.
Perelman has been a fan of the hawks since their first nest at the Franklin. "I will confess to having taken an unduly large interest," she said. Given that this is a science museum, "we're just so lucky that they've come to live with us."
Now, the young hawk will have to "take his chances, like everything else out there, but we think he's going to do well," Schubert said.
Will he find his way back to his parents?
Now empty nesters, they have been availing themselves of some choice spots, perching atop an Art Museum griffin and bathing in the reflecting pool at the Barnes Foundation.
It's unlikely that Peanut will return to his parents' urban digs, Schubert said. "At this age, he would be striking out on his own anyway," at some point finding a mate and continuing the line of the Franklin hawks.
Contact Sandy Bauers at 215-854-5147, firstname.lastname@example.org, or follow on Twitter @sbauers. Read her blog, GreenSpace, at www.inquirer.com/greenspace