Young hearts still beat in Falcon eggs rescued from Bay Bridge
Published: April 16, 2007
A team of biologists recovered a clutch of peregrine Falcon eggs nested on the central anchorage of the San Francisco-Oakland Bay Bridge late Friday morning after high winds stymied recovery attempts earlier last week.
Two of the three speckled, brown hen-sized eggs were viable, meaning there’s a chance they could hatch, said Glenn Stewart, a research associate at the University of California, Santa Cruz’s Predatory Bird Research Group.
Biologists from the bird research group will incubate the two-week-old eggs, which have a 34-day gestation period, at the organization’s research facility in Santa Cruz, Stewart said.
The nest site on the bridge would have been a lethal one for fledgling birds, who would have headed into the water on their first flight, he said.
Falcon eggs have hatched on the bridge in the past, but “it’s a dirty, vibrating environment” that, unlike the falcon’s natural cliff habitat, is not particularly conducive to survival, Stewart said. It takes six weeks for the young birds to grow feathers adequate for flying more than short distances, he said.
Biologists from the UCSC team that led Friday’s rescue effort are hoping Gracie, the falcon who laid the eggs on the span, will lay another clutch within two weeks or so in a safer spot somewhere in downtown San Francisco.
“I hope they don’t do it up there,” Stewart said of Gracie and her mate George. Peregrine falcons are territorial and often return to lay eggs in the same place, he said.
Gracie and George have lived in downtown San Francisco for around five years, Pacific Gas and Electric Co. spokesman Brian Swanson said.
Last year the pair set up house and laid four eggs in a planter at 201 Mission St., he said.
From 2003 to 2005 Gracie laid eggs in a nest on top of the PG&E building at 77 Beale St. and in 2005 PG&E set up a Webcam to allow fans and UCSC researchers alike to observe the birds.
The utility also paid for today’s recovery, Swanson said.
Peregrine falcons have used 77 Beale St. as a perch since the 1980s, according to Swanson.
Friday’s recovery effort was led by Brian Latta, one of a team of biologists on UCSC’s predatory bird research team.
If the eggs recovered Friday end up hatching, they will be placed with a foster mother and handfed before being released off the California coast to find their own territory, according to Swanson.
Another clutch of eggs on the Oakland end of the span will have to wait to be rescued, Stewart said.
According to Stewart, there are five or six pairs of peregrine falcons in the Bay Area.
“That means that the area is rich with wildlife and birds in particular, because they eat birds,” he said.
“Pigeons would be a common-sized food … but it ranges all the way from starling to Western
gulls.”
The Oakland pair and George and Gracie can live in such close proximity because of Treasure Island, which effectively divides each pair’s territory.
Visual barriers and the amount of food available in an area, rather than distance, determine falcons’ territorial boundaries, Stewart said.
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