For me sparrow identification is right up there with gull identification as far as difficulty goes. I think that part of the problem is that sparrows are not very large, which makes it more difficult to see their tiny field marks. The fact that they almost never seem to stand still also does not help.
Fortunately, if you are able to catch a pic or two it makes it much easier to ID them. I photographed this field sparrow near the Old Cedar Ave bridge in September. It can be identified by the stout pink bill, white eye ring and the gray and rufous pattern of the head. It resembles the American tree sparrow except that the tree sparrow has a bicolored bill and a dark spot on the breast.