Swarms of Swifts in San Rafael October 7, 2012Posted by GGAS in Birding
By Rusty Scalf
The birds seem to come out of nowhere. Literally. The late afternoon sky is blue, with a few clouds, a few gulls, a couple of Ravens. Then I notice two tiny bat-like creatures well above the old smoke stacks.
Bat-like but not bats. Swifts. Tiny, gray, fast, erratic.
Then a group of five heading the same way meet the two and coalesce like little droplets to seven, then disappear. And so it begins. Fifteen minutes later there are perhaps 300 in a gnat-like swarm. Ten minutes more it’s 600 that decide, for a short while, to emulate a lava lamp, a tight morphing blob of birds, only to scatter to gnat-like entropy once again.
The light becomes long, the sun is just above the hills to the west, and the swifts keep building. Eventually they’re a vortex, swirling around the complex a couple hundred feet up. As the light begins to fade, the scene above the old smoke stacks is other-worldly. The thousands of birds now make estimation a dizzying prospect.
My goal is to estimate how many swifts are present. Impossible really. The best one can do is follow a set protocol and hope for consistency. The task: train a scope on the top of a stack, click-counter in hand, and click once for every ten (or some gestalt sense of ten) swifts that enter. Entry rate seems to peak at approximately ten birds per second into the favored north stack.
A joint Golden Gate/Ohlone Audubon outing on Sept. 22, 2012 recorded an estimated 19,500 birds! Double the highest previous count! The number of birds at the stacks rises and falls, often dramatically, day by day. Larry Schwitters, who tracks the West Coast migration of Vaux’s Swifts, estimates (based both on Chimney Swift banding data and his own census numbers) that typical residence time at a migratory roost is 3-4 days within a range of 1 to 7 days. At McNear Brickyard here in San Rafael, September counts of 500 to 10,000 have been typical. More than 19,000 was just over-the-top. Lucky, eh? Every once in a while…..
Vaux’s Swift is the smallest North American swift species, about 4.75 inches long, and closely related to the eastern Chimney Swift. Both species evolved to nest in large hollow snags, which have almost entirely disappeared in the east and become ever more scarce in the west. So Vaux’s Swifts are undergoing the same conversion to chimney nesting as did their congener 150 years ago, with more and more colonizing residential chimneys in the Pacific Northwest every spring. This year Santa Rosa birder Gordon Beebe found a pair nesting in his chimney, and the birds were successful!
During fall migration, swifts gather in large-to-huge communal roosts, migratory “staging” sites. One Vaux’s roost is a large redwood snag in Humboldt County, the last known natural staging site. Most of the population seems to be “imprinted” on large antique chimneys, some of which are industrial in scale. Presently there are four in Washington and four in Oregon hosting tens of thousand of birds each fall. Until 2010 the only known Northern California chimney site was at the Rio Lindo Academy in Healdsburg, 60 miles north of the Golden Gate. Together the snag and the chimney were the only known staging sites north of Los Angeles.
In 2009, I was asked by Steve Lombardi to help investigate rumors of Vaux’s Swifts roosting at Pinnacles National Monument. Steve and I made several trips and found thousands of White-throated Swifts, but no Vaux’s. Pinnacles is famous for the cliffs favored by White-throated Swifts but has none of the large hollow snags or chimneys preferred by Vaux’s.
Larry Schwitters – who was our GGAS guest speaker in September — was the man who had recruited Steve and me to check out the Pinnacles. I spent some time looking at photos on his web page of the eight big chimneys in the Pacific Northwest that host staging Vaux’s Swifts.
Then, in June 2010, I found myself in San Rafael wanting to go north, and decided to take the coast route rather than the freeway. I hadn’t been on Point San Pedro Road in years. While driving I saw the McNear Brickyard stacks, stopped and stared. Wondering. I decided to return in September.
September 17, 2010… I returned, arriving late evening with no particular expectations. Got out of my car, looked up at the stacks, and just about had a coronary. A huge vortex of swifts was circling the chimney!
McNear Brickyard, with its tall chimneys that were decommissioned in 1962, is the first and only Vaux’s Swift staging site found in the immediate San Francisco Bay Area. It currently hosts hundreds to thousands of swifts on September nights, with dwindling though still substantial numbers into early October.
Some estimates from the past couple of Octobers:10/2/2010 6,000 10/6/2010 9,000 10/8/2010 5,000 10/9/2010 6,300 10/16/2010 60 10/1/2011 5,300 10/7/2011 5,000 10/8/2011 1,000 10/10/2011 1,000 10/13/2011 320 10/2/2012 3,800 10/4/2012 3,300 10/5/2012 2,990 10/7/2012 2,920
To view the swifts: At this time of year, arrive before 6 p.m. The brickyard is 4 miles along Point San Pedro Rd., north of the Central San Rafael exit off of Hwy 101. On Mapquest or Google Maps, you can use the address of 1 McNear Brickyard Rd., San Rafael, CA 94901. If you are willing to count, please do so and email your results to Rusty at firstname.lastname@example.org.
Of course, like everything else in birding, there is no guarantee that the swifts will be there. To view a video of Vaux’s Swifts arriving at a chimney in Los Angeles, see
Rusty Scalf, a GIS (computer mapping) expert, has been teaching a Bird Identification class for Golden Gate Audubon and Albany Adult School for nearly 25 years. He has also been a field trip leader and Christmas Bird Count area leader for Golden Gate Audubon, and has been a field volunteer and map maker for the Breeding Bird Atlas movement (Alameda, Contra Costa, Solano, Yolo counties, and now Sonoma County).
Photos by Kerry Wilcox. You can view Kerry’s online gallery at http://www.flickr.com/photos/9587960@N03.Tags: Bay Area birds, Larry Schwitters, McNear Brickyard, migration, roosting sites, swifts, Vaux's Swifts.