Still trying to key out the bird that I thought was a black-and-white warbler, then thought was an unusally dark female house finch.

It came to the window feeder a couple of times during the few days of really cold and snowy weather we had. Small, slender bird. Long, thin, slightly curved, black beak. buff-to-yellow rump patches visible when it takes flight. No yellow on wings that I could see. Too far north to be a black-and-white warbler. Possibly a yellow-rumped warbler. Haven't seen it since the weather warmed up and the snow melted.