Peregrine falcon eggs on San Francisco high-rise about to hatch

UCSC Predatory Bird Research Group keeps watch via web camera

peregrine falcon on nest
A female peregrine falcon known as "Diamond Lil" shifts position on her nest at PG&E's headquarters in San Francisco's financial district Wednesday afternoon. The four eggs are expected to hatch any day. UCSC's Santa Cruz Predatory Bird Research Group has been instrumental in reintroducing peregrin falcons to the wild over the past several decades. (Photo from

Four peregrine falcon eggs in a nest at the San Francisco headquarters of PG&E are expected to hatch any day, according to Glenn Stewart, director of the UC Santa Cruz Predatory Bird Research Group (SCPBRG).

The eggs are in a nesting box located on a ledge of PG&E's building in the financial district. Hatching is expected to begin today (March 28) based on Stewart's calculations from when the first egg of the 2012 season appeared February 19.

Incubation usually begins after the arrival of the third egg and lasts approximately 33 days, Stewart said. The fourth egg hatches a day or so after the others.

Early Wednesday afternoon, a nest web camera showed the mother peregrine known as "Diamond Lil" still sitting on her nest.

The Predatory Bird Research Group, based at UCSC's Long Marine Lab, successfully reintroduced peregrine falcons to the wild after the species was nearly decimated 40 years ago from the effects of the pesticide DDT.

Stewart said PG&E has partnered with SCPBRG for decades, including helping UCSC host the nest web cameras that are live and run continuously throughout the year.

"PG&E has been a terrific host to the birds since we established the first nest camera in 2005," Stewart said. In addition, PG&E helps underwrite the conservation education assemblies that SCPBRG puts on for schools throughout Central and Northern California.

As hatching approaches, Stewart said, webcam viewers are expected to see the mother rise up off the eggs and look at them when she hears cheeping from within the intact eggshells. A "pip" or barely discernible puncture of the shell will be the first evidence of hatching but won't be visible on camera. Each chick will rest for many hours after pipping before beginning to cut its way around the equator of the egg toward freedom.

The mother will begin to feed the young small bits of food within hours of hatching,
though the egg yolk will continue to nourish them for about a day.

The PG&E peregrine falcons have been a San Francisco financial district institution since the first falcon nest camera images appeared online. The falcons achieved a following from around the world including more than 300 schools and attracted more than one half million hits per week on the SCPBRG website. 

Stewart said many volunteers in the falcon recovery project began as interested viewers.
 “Many of the people who began as online falcon-watchers are today as valuable to our study of this species as the paid staff members we once employed to assist with the Peregrine Falcon Population Recovery effort,” Stewart said.

When the chicks are two to three weeks old, Stewart will go to the nest site to place identification bands on their legs. UC biologists are interested in the dispersal of falcon fledglings from natal areas to eventual nesting territories, the longevity of individuals, and tenacity of pairs at the nest site.

The young birds are able to fly and usually fledge after 41 to 44 days of growth, Stewart said. Volunteers are invaluable during the fledging period to help keep the babies safe should they end up on the ground. "We just put them back up on the nest ledge to have another try," Stewart said.

Falcons have been associated with the PG&E building since 1987 when the first nest box was installed. They have used the building intermittently for nesting since 2003.