Update 1:40 p.m. Okay the big event appears to be over. But that doesn’t mean you shouldn’t click on the webcam and gawk…

Original post SAN FRANCISCO – (Bay City News) Bay Area residents will soon know the sex of four peregrine falcon chicks that hatched on a ledge of the PG&E building in downtown San Francisco several weeks ago.

Glenn Stewart, director of the Predatory Bird Research Group at the University of California at Santa Cruz, is preparing to walk out onto a protected ledge on the 33rd floor of the building at 77 Beale St. and band the baby birds at 1 p.m. today.

Stewart explained that during the banding process, he examines the depth of the birds’ heel bones to determine their sex.

He said he doesn’t expect the chicks’ parents to appreciate the visit.

“The adults complain bitterly while we’re out there,” Stewart said. “They fly back and forth — and make a lot of noise.”

However, he said, the banding only takes about 15 to 20 minutes and amounts to a minor inconvenience for the birds.

When the banding is over, Stewart said, “They feel like they won, like they drove us away.”

PG&E spokesman Joe Molica said the young falcons will each get bands on both of their legs. One is a U.S. Fish and Wildlife Service band containing a phone number people can call if they find the bird; the other is an identification band that can be read from a distance by someone using binoculars. The bands allow researchers to track and learn more about peregrine falcons, which were once endangered.

Stewart pointed out that today’s banding comes one day after Earth Day, which he identified as one of three major milestones in the decades-old effort to protect birds like the falcons. Along with Earth Day, which began in 1970, Stewart identified the two other milestones as the 1972 banning of DDT — which he said had caused the thinning of birds’ egg shells — and the passage of the Endangered Species Act in 1973. He said that in the early 1970s, peregrine falcons were on the verge of extinction, but that they have since made a great comeback, thanks in part to efforts by the UC Santa Cruz bird group and researchers at Cornell University.

Another group of baby falcons that hatched on a ledge at San Jose City Hall earlier this month is set to be banded on May 1. Stewart said he expects the San Francisco chicks to begin to fly sometime around mid-May, followed by the San Jose chicks.

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