September 23, 2011
This past Monday a few of us embarked on a real urban nature adventure. We traversed the city streets of Los Angeles to witness one of the coolest nature spectacles I have ever seen in downtown Los Angeles, 6,500 Vaux's Swifts, Chaetura vauxi, spiraling into an old building shaft!
Ghetto bird and swifts share L.A.'s skyline alike!According to Kimball Garrett, NHMLA's Ornithology Collections Manager, these swifts stop in L.A. during their spring and fall migrations to and from their breeding grounds in the Pacific Northwest and their overwintering sites in Mexico and Central America. While in L.A. they gorge themselves during the day on flying insects found in areas such as the L.A. river and Griffith Park, and roost at night in various shafts and chimneys around the city.In recent years the roost of choice for thousands of these birds is the Chester Williams building, on the northeast corner of Broadway and 5th Street, near Pershing Square. The parking structure next door to this building is where myself and a few other Museum staffers found ourselves at 6:00pm on Monday evening. At approximately 7:30 the swirling masses of swifts began entering the shaft. Although it is impossible to count every individual, Kimball was able to estimate the number of birds entering the roost site. They enter the shaft at a remarkably constant rate of about 10 birds per second. We watched birds enter the roost for about 11 minutes (660 seconds), yielding a rough estimate of about 6,500 birds. Thanks Kimball!
Vaux's Swifts spiraling into the Chester building's shaftOf course Sam Easterson was one of our party, he managed to capture this footage of the swifts entering their roost.As a final note, its not all easy living for the swifts. Common Ravens, Corvus corax, have learnt to hang out at the shaft opening and prey on individuals entering their roost site. I managed to catch a picture of this Raven flying away with its dinner!
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