Biologist bands 2 peregrine falcon chicks perched at San Jose City Hall

SAN JOSE, Calif. -- A biologist banded two peregrine falcon chicks perched at San Jose City Hall Tuesday but faced some aggression from the birds' parents that were alarmed by a human presence.

The chicks, a male and a female, were born to parents Clara and Fernando El Cohete three weeks ago, said Glenn Stewart, director of the University of California at Santa Cruz Predatory Bird Research Group.

Stewart rappelled 40 feet down to the family's nest on a ledge on the south side of the 18-floor City Hall Tower this morning.

He placed bands on the chicks that will be used to keep track of them once they start to fly, which isn't expected for another three weeks.

The newborn chicks' bodies have fully grown but they're having a hard time standing up, Stewart said.

The chicks' parents were flying at about 100 mph around the nest while Stewart was up there and it was a surprise when one them struck his helmet a couple times.

"Their job is to drive me away and they go back to being parents," Stewart said.

The ledge measures 5 feet wide and 20 feet long and is inaccessible from the building, he said.

Clara adopted the City Hall Tower as her home soon after the building opened in 2005 and first gave birth about two years later, Stewart said.

There have been 34 hatchings at the City Hall Tower since 2007, according to Stewart.

Peregrine falcons were taken off the critically endangered list in 1999 and live for about 10 to 15 years, Stewart said.

The research group has a partnership with the city to provide advice on the falcons, study the birds and educate the public on the species.

Click here to check out the live falcon camera.