Unita, the only female among four recently hatched falcon chicks, died on Sunday afternoon as she attempted to fly for the first time, said Glenn Stewart, coordinator of the University of California at Santa Cruz's Predatory Bird Research Group.
She tried to go after a dead pigeon her mother had brought to feed the falcons, but because her wing feathers had not fully developed, she crashed into the rotunda before reaching her meal, Stewart said. She was 40 days old.
Gail Downey was one of a dozen people who expressed condolences on a Facebook page created for the falcons.
"Very sad," Downey wrote. "We all become so attached to each one as we watch them grow. It is sometimes difficult to remember they are wild and part of nature, which is not always kind. I will miss her."
Stewart echoed Downey's message.
"These things happen," he said. "People need to understand that every baby doesn't survive."
Unita was born in April on a City Hall ledge 18 stories above the street, along with three male chicks, Hermes, Shadow and Ahote'.
Names for all four were suggested by San Jose schoolchildren in an online contest.
This is Clara's fifth nesting season at City Hall and her third with mate Esteban Colbert.
The FalconCam, a live streaming video of the falcons' nest, can be viewed on the city's website at http://www.sanjoseca.gov.