Migrating Swifts Take Over LA Parking Garage As many as 10K a night sleep over en route to breeding grounds By Caroline Miller, Newser Staff Posted Apr 24, 2010 7:11 AM CDT 3 comments Comments Vaux's swifts (Flickr) (Newser) – A 12-story Los Angeles parking structure has become an unlikely pit stop for an astonishing number of migrating birds, with tens of thousands of them holing up in an abandoned brick chimney overnight en route to breeding grounds in the Northwest, British Columbia and Alaska.The birds are Vaux's swifts—4 1/2 inches long and cigar-shaped, the Los Angeles Times reports—and they started appearing at the Chester Building about a week ago. The nightly show of birds filling the air and funneling down the chimney has brought out not only swift watchers but ravens, who snag the swifts as they head down. "It's like watching bears grab salmon out of a river—where's the 12-gauge shotgun?" lamented one watcher. Experts say the site is one of the most significant roosting sites for these birds. "Sites with more than 10,000 Vaux's swifts are very rare," says one tracker. "There are only about six of them in the world."