Scientists have identified four peregrine falcon chicks that hatched on a ledge of the PG&E building in downtown San Francisco several weeks ago as two males and two females.
Glenn Stewart, director of the Predatory Bird Research Group at the University of California at Santa Cruz, walked out onto a protected ledge on the 33rd floor of the building at 77 Beale St. to band the baby birds Monday afternoon.
Stewart explained that during the banding process, he examines the depth of the birds' heel bones to determine their sex.
"You measure the heel bone -- it's a long yellow leg bone that we put the band on," Stewart said, adding that the female chicks are a third larger in body size than the male chicks. "They will be fledgling around the 10th of May. They will hang around for a month and eventually they will find their own place." Stewart said. "Peregrine means wanderer in Latin."
Stewart 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.
Those interested can watch the falcons live online via the bird research group's "falcon cam" at http://www2.ucsc.edu/scpbrg/nestcamSF.htm.
Scientists on May 1 will band another group of baby falcons that hatched on a ledge at San Jose City Hall earlier this month.
Stewart said he expects the San Francisco chicks to begin to fly sometime around mid-May.