Espie and her brother Hiko fledged from the San Jose City Hall nest in 2007–Clara’s founding year in her territory. Hiko settled at the Fruitvale Avenue Bridge territory and Espie, the East Span of the San Francisco-Oakland Bay Bridge.
The East Span territory has been used in the post-DDT era since 1983 when a blue-banded pair (peregrines released by SCPBRG) appeared. The male had been fostered into a Napa County eyrie and the female cross-fostered into a San Luis Obispo County prairie falcon eyrie. The female was shot near the nest and while peregrines were seen on the span for several years, breeding was not documented until 1990.
The peregrines preferred a nest site that was a little alcove in “E-2″ the second tower east of Yerba Buena Island about thirty feet below the eastbound roadbed. This north-facing metal box contained enough dirt, gravel, and road debris to support incubation and nesting attempts were made in many of the years after 1990.
Our observers documented all manner of calamity when the young attempted fledging. Peregrines are clumsy at landing during their first few days on the wing and the East Span of the Bay Bridge offers scant perching structure to a young peregrine. Sometimes they were carried upward on the strong wind out of the north and then clambered for a perch alongside the roadbed and were squashed by a speeding vehicle. Other times they were set upon by gulls and driven into the sea where they drowned.
A unique agreement was reached whereby the young could be moved to a safer fledging environment during seismic retrofitting construction following the 1989 earthquake. We moved young from the bridge for years. The agreement allowed construction to go forward where a state-endangered species was nesting and it was very good for the birds because their young had a 95% chance of drowning if left in place. When the seismic retrofit construction was complete and state-endangered status removed (2009) the agreement to move young expired.
Today, lands immediately adjacent to the San Francisco Bay probably have more peregrine falcon territories than at any time in history. Their speedy recovery from near-extinction in our state is due first to stopping the use of DDT and then to recovery activities. But the Bay Area population density can only be explained by the appearance of modern structures offering nest ledges on bridges, buildings, and cranes, and the presence of a booming non-native rock dove (pigeon) population. Nest sites average less than 5 miles distance between them in some parts of the Bay Area and this year a sample of 12 nests yielded an average 3.0 young per nest that were at least 25 days of age.
The peregrine falcon population is robust but I do not think that is a good reason to look the other way when a recent candidate for extinction will very likely fledge its young into the sea. We brought them back from extinction. We put up the nesting habitat. And, we introduced the abundant food source that now sustains them. I think we bear some responsibility to give them a chance at safe fledging and I have fought that fight for years. But what we (those of us who love peregrines) are up against is an agency-wide wildlife non-intervention policy. That policy, coupled with a species that is now abundant, makes it very difficult for us to gain an exemption.
An additional caveat making it especially hard to do the right thing for bridge-nesting peregrines is this: The State Department of Fish and Wildlife established a policy whereby peregrines may not be hacked (released) less than 50 miles from the coast (a protection for snowy plovers & California least terns–a decision based on emotion and not science in my opinion) or, in the habitat of the greater sage grouse. With this policy the State has pretty much eliminated suitable habitat for peregrine releases. Thanks to an accommodation by colleagues at UC Davis, I was able to gain approval for a release site at one of their off-campus animal facilities that was useful for early season peregrine fledging, and I used that site successfully last year.
The end of the story about Espie and her young is this: The old East Span is being dismantled this year so the agencies changed their mind about non-intervention and agreed to allow me to move Espie’s young. But, in a particularly bone-headed move, CalTrans sealed off the favored E-2 nest site in mid-February thus throwing off the breeding cycle. A little later the pair appeared to be making an attempt to nest on a corner gusset plate that anchors a girder to a tower, and finally, quite late in the breeding season, they settled in a cavity low on the E-8 tower.
Knowing that temperatures would be exceeding 100 in Davis by the time the young were ready to fledge (it is forecast to be 101 today) I cancelled plans to have any part of their translocation. Putting peregrines inside of a box on the top of a roof in 100 plus degree heat just might be worse than fledging from the Bay Bridge. What I do know is that a peregrine tortured with enclosure in a hot box for a week would probably never return to the box for food and quickly starve. It was frustrating to be able to take them but unable to release them in a manner that was up to our standards. Their chances on the bridge? Probably not good either. An industrial area to the south may offer them a perch. A short distance to the north is the speeding traffic of the new east span which is certainly lethal. And then there are the gulls.
Observers may ride a bicycle or walk out the bike path on the new East Span to view the birds on E-8 (count 8 towers from the island). Some folks report getting quite close to Espie and her mate while they are perched on the new span. The young should be fledging any day now. Personally, I do not want to witness the calamity.
(Post Script: We withheld information about the E-2 nest location because the area was closed due to bridge construction activity).