The feat by University of California, Santa Cruz biologist Glenn Stewart has become a tradition known as San Jose's Annual Falcon Banding Day, where wild falcon chicks have hatched in the nestbox since Stewart installed it in 2007, Mayor Chuck Reed spokeswoman Michelle McGurk said.
Stewart used ropes to ascend from the roof of city hall to reach a ledge holding the nestbox, affixed a band onto the leg of each chick and revealed the sexes of the four birds, two males and two females, McGurk said.
Once the chicks, known as eyasses, learn how to fly and leave the nest, scientists and bird watchers will be able to read their bands to identify them for research purposes, McGurk said.
While Stewart banded the chicks, the mother and father peregrine falcons, named Clara and Fernando, swooped up and down in the air and made loud shrieking noises in attempts to protect their young from what looked like a predator, McGurk said.
"They were quite active in defending the nest, they flew around quite a bit, some spectacular dives," McGurk said. "It was amazing."
"They come close, but they don't actually attack (Stewart)," McGurk said. "They are quite vocal."
The chicks hatched over two days, April 8 and 9, bringing to 29 the number of eyasses produced in the nestbox in the last seven years.
The city has already held a contest for San Jose public school children, aged 5 to 18, to nominate names for the young birds and city will announce the chosen names shortly, McGurk said.
San Jose Peregrine Falcon Alliance, made up of volunteers who look after the birds at city hall, selects the names of the adult peregrines that arrive at the nest, according to McGurk.