Saturday evening we were driving north on Capitol Blvd. in Tumwater and, as we passed between the two sections of the former Olympia Brewery, my wife said, "Look at all those birds flying around the chimneys. Are they bats?" Swifts immediately came to mind. We turned around and observed hundreds of swifts swarming around the two metal chimneys to the east of Capitol Blvd. We parked about a block away and watched the swifts until about 9:15.
I returned last night and walked out on the bridge over the Deschutes River so I was within 100 yards of the chimneys. The swifts appeared in small numbers around 8:30 but only swelled to about 200. By 8:40 they were all tucked into the metal chimneys.