Every fall an aerial spectacle takes place high above the Marin Headlands across the Golden Gate from San Francisco.  Between late August and mid-December, thousands of migrating birds of prey, called raptors, funnel southward over the Marin peninsula to its southern tip.  With a good tailwind, some zip across the Golden Gate right away, while many others congregate temporarily above the headlands on rising thermals and updrafts to gain altitude before resuming their southbound heading.

For the past 25 years, the citizen-driven Golden Gate Raptor Observatory (GGRO), an arm of the Golden Gate National Parks Conservancy, a partner of the National Park Service at Golden Gate National Recreation Area, has kept track of the biggest hawk migration in the western United States each fall.  The GGRO’s Hawkwatch program, designed to detect daily and seasonal migration patterns and to monitor long-term population changes, has shown that up to 19 species of raptors pass over the Marin Headlands during migration.

Traditional scientific tools such as binoculars, traps and radio transmitters have allowed volunteers to count a thousand hawks a day, to band dozens a day and to follow a hawk to Mexico.  Other innovations for raptor study  include a standardized group-counting technique for "measuring" daily flights, a mechanical bird to lure hawks into traps for banding and the first calibrations of West Nile Virus infection rates in California’s wild raptors.

 

The GGRO today makes use of 300 volunteers annually and draws some 10,000 visitors to the headlands each autumn.  Allen Fish, director of the GGRO since its inception in the early 1980s, will chronicle both the observatory's citizen contributions and its avian splendors in a slide presentation, “Twenty-five Years of Raptor Gazing at the Golden Gate,” at the Yosemite Area Audubon Society’s monthly program Thursday, May 8, beginning at 7:00 p.m.  The program will be held at the Mariposa Methodist Church parish hall on 6^th Street between Highway 140 and Bullion Street in downtown Mariposa.

A dynamic and entertaining speaker, Fish will tell tales of reverse migrations, of a nearly domesticated red-tailed hawk and of a Bay Area city with the highest density of nesting Cooper’s hawks ever recorded.  A Redwood City native schooled at the University of California at Davis, Fish now teaches raptor biology there every winter and consults on avian conservation issues throughout the state.  He lives in Berkeley with his wife, an art librarian, and “two kids who can’t have dessert,” he says, “until they can tell a sharpshin from a coop.”

Like all Audubon programs, Fish’s presentation is open and free to the public, although donations to defray program costs and to support Audubon’s local activities are welcome.  Refreshments will be available.

Yosemite Area Audubon’s monthly birding trip will be to Yosemite Valley and Foresta on Saturday, May 10.  [Note: This date is in lieu of the trip originally scheduled for May 17.]  Participants will meet at 8:00 a.m. at the Midpines County Park to carpool.  The trip is free and the public is welcome.  Bring binoculars, field guides, lunch and beverages.

Call (209) 742-5579 for additional information about either the program or the birding trip.

The Yosemite Area Audubon Society is affiliated with the National Audubon Society.  Both the national organization and the local chapter are dedicated to the preservation of natural habitats and native species, and to educating and inspiring others to help protect those resource values.