[cobirds] Black Swifts over CU Boulder campus

While walking across the CU-Boulder campus a few minutes ago, I saw two swifts flying over the Dalton Trumbo fountain area.  Larger than Violet-green Swallows, fully dark, lacking even a paler throat, slower wingbeats, and totally silent led to my conclusion that these were Black not Chimney Swifts.  It is not unusual for Black Swifts to come to lower elevations when summer days get as cold and low-ceilinged as today is.