The Pine Siskin is a small, goldfinch-like bird with a distinctive “zipper” call. It is one of the few birds on That Yard’s list identified solely by sound. To hear it yourself, click the preceding link, go to the “Sound” tab, and play the “zhreee” call.
Pine Siskins are common winter visitors in southern Wisconsin, though their migration patterns can be erratic. It remains to be seen whether more will arrive.