Presidio of San Francisco (February 5, 2009) -- A bird in the hand, in this case, is worth more than 7,000 in the bush. About a dozen birdwatchers recently fanned out across the Presidio for the annual census of the park's bird population. Trekking through almost every neighborhood and district in the park they spotted everything from large hawks (12 Red-shouldered hawks) to tiny songbirds (117 Ruby-crowned Kinglets). Those out in the earliest hours of the morning heard the park's four resident Great Horned Owls. And off the Coastal Bluffs, birdwatchers counted 1,309 Western Gulls and 1,187 Western Grebes. All told, birders counted 7,301 birds representing 111 different species.
It is believed that about 200 bird species use the Presidio, ranging from year-round residents like Anna's Hummingbirds, Red-shouldered Hawks, and Great Egrets to migratory species like Violet-green Swallows and Red-throated Loons.
The numbers from the Presidio's bird count were added to the totals for the broader San Francisco bird count, which encompasses an area of 177 square miles from San Bruno to the Golden Gate Bridge and from Yerba Buena Island to Fort Funston. Scientists use the data to discover how bird populations are changing, usually in response to changes in land use and habitat caused by humans. For instance, in eastern North America, data has shown a startling decline in bird populations, an early warning sign of possible environmental problems throughout their range.
The Audubon Society has been conducting such counts since 1900. The first one in San Francisco was conducted in 1915.
"The goal is not to have an exact number of all the birds, like say a rancher would count how many head of cattle he has in his herd," says Andy Kleinhesselink a biological science technician with the Presidio Trust. "Rather it is to get an overall sense of how abundant birds are in the Presidio, in San Francisco or in whatever area the count is being done."
"Since the counts are done at the same time and in the same places every year," Kleinhesselink continued. "And since there are hundreds of them across the nation, in general they are an accurate way to track bird populations on a regional or national scale."
Among the other significant findings in this year's count:
Only one Surf Scoter, a common sea duck, was found around the Presidio. Surf Scoters usually number in the hundreds and speculation is the precipitous drop in their population may be the result of the November 2007 oil spill in the bay.Four Wrentits were observed along the Coastal Bluffs, giving hope that the species, which nearly became extinct in San Francisco the last few years, can find refuge and survive in the natural areas of the Presidio.Three Yellow-headed Blackbirds were spotted flying south high over the Presidio. Though common in other parts of California, it is extremely rare to find the yellow-headed blackbirds in San Francisco and on the coast in general.
For a complete count visit:http://www.audubon.org/bird/cbc/index.html.
The Presidio Trust was established by the United States Congress in 1996 to oversee the Presidio of San Francisco, an urban national park located at the base of the Golden Gate Bridge. The 1,500-acre site contains expansive open space and spectacular views, a 300-acre historic forest, and rare and endangered plants and wildlife. It also comprises nearly 6 million square feet of buildings, including 469 historic structures that contribute to its status as a National Historic Landmark District.