We've had as many as 25 Pine Siskins coming regularly to our feeder. They are braver than most birds and will remain at the feeder even if we walk relatively closeby, whereas the Lesser Goldfinches flee earlier. It's also amazing just how much they eat. They will remain perched at the feeders for prolonged periods eating the whole while. I've also noted that they will frequently eat fallen seed from the ground, something I had not seen them do elsewhere.
The more you look, the more you see. Today I was struck by the difference between these two males. The one on the top left is the subspecies I mostly see, with relatively little yellow and darker streaking. The one on the bottom right has obviously more yellow and much lighter streaking.