Researchers Take Eggs From Bay Bridge Falcon Nest
Mar 30, 2007
CBS Broadcasting Inc
Raw Video: Falcon Egg Rescuer Helmet-Cam
Raw Video: Biologist Transfers Eggs To Incubator
Raw Video: Peregrine Falcon Egg Rescue(CBS 5 / AP / BCN) SAN FRANCISCO A peregrine falcon shrieked in vain Friday as scientists snatched three eggs from his precarious perch beneath the central anchorage of the Bay Bridge in an attempt to save the chicks from a deadly fall or car collision when they hatch.
"It's the most dangerous place in the world for them," said Brian Latta, a University of California, Santa Cruz, biologist who removed the eggs from a narrow beam about 200 feet above San Francisco Bay.
The parents, dubbed George and Gracie, had nested for years on the 33rd floor ledge of Pacific Gas and Electric Company's downtown San Francisco skyscraper at 77 Beale St., where they raised several clutches of chicks. The pair relocated to the bridge this year at the same spot where George hatched in 1999 and was rescued in a similar operation before he was old enough to fly.
If the eggs were allowed to hatch under the bridge, crosswinds could send the fledglings plummeting into the bay or hurtle them under the wheels of passing cars when they left the nest for their first flights. In fact, high winds stymied previous egg recovery attempts on the bridge by scientists earlier this week.
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, said UCSC research associate Glenn Stewart. It takes six weeks for the young birds to grow feathers adequate for flying more than short distances, he explained.
Latta moved in Friday after Gracie left George alone to defend the nest, a two-inch depression in a wind-blown pile of dirt. Peregrines are known for their ferocity when their nests are invaded, and George swooped and circled as the eggs were taken.
"When the female comes back, he's going to have a lot of explaining to do," Latta said.
The couple are celebrities among San Francisco bird watchers, who have followed their progress in past years via a Web camera near the previous nest at PG&E's city headquarters. Peregrine falcons have used 77 Beale St. as a perch since the 1980s, PG&E spokesman Brian Swanson said. The utility also paid for the cost of Friday's bridge egg recovery effort.
The peregrine falcon, which can reach speeds of more than 200 mph in its hunting dive, has taken up residence in many U.S. cities. Tall buildings mimic the steep cliffs that are the birds' natural habitat, and pigeons provide a plentiful source of food.
By removing the eggs from the bridge nest, scientists hope George and Gracie return to their old downtown nesting site - a much safer spot - and lay new eggs within a few weeks.
"I hope they don't do it up there" on the bridge again, Stewart said. Peregrine falcons are territorial and often return to lay eggs in the same place, he explained.
A digital monitor detected a heartbeat in two of the three speckled, brown hen-sized eggs removed from the bridge - indicating they were viable. The eggs were packed in foam in separate plastic tubes after the rescue.
Biologists at the university's Predatory Bird Research Group planned to incubate the two-week old eggs, which have a 34-day gestation period, and turn the hatchlings over to adoptive peregrine parents until they are ready to return to the wild. At that point, the young birds will be released off the California coast to find their own territory.
Another clutch of eggs on the Oakland end of the Bay Bridge span will have to wait to be rescued, Stewart said.
While the raptor was removed from the federal government's endangered species list several years ago, it remains fully protected under California law.
There are currently an estimated 250 peregrine falcon nesting pairs in California, and Stewart said there are five or six pairs 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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