EDIT 2/26/20 -- I got a closer look when they moved to the south lot and I could see more different types of fieldmarks on individual birds. :D So at least a substantial number of these are natives, not invasives. They're skittish and at once point they startled, filling the air with black and red wings. \o/
EDIT 2/26/20 -- I went outside and fed the birds. More snow is melting, some icicles forming. The big flock is gone but I heard cardinals calling.