Well, maybe it won't be a challenge for these 2 bird experts, and anyone else who would like to join in. I was enjoying the wing marks and tracks left in the snow when I was out cross country skiing last week. So paul, can you ID birds by their tracks? Maybe this is really easy, I don't know. Since there is nothing in the photo to give you a sense of scale, let me point out one clue - the camera was held on the diagonal; the horizon is up in the top left corner, obviously not levelled. Oh, and I'm in Calgary, Alberta.
Spike