American Tree Sparrow (#5) and Field Sparrow (#6)

American Tree Sparrow digging in the snow looking for birdseed fallen from the front yard feeder; 1-10-10.

All spring I was misidentifying Field Sparrows as American Tree Sparrows, until I realized two main differences. First, at about the same time the Field Sparrow is returning to Northern Illinois from its winter home just a bit south from here, the American Tree Sparrow, which spends the winter here is already on the move to its tundra breeding grounds in Alaska and Northern Canada. To me they look very much alike which caused my misidentification of the two. Secondly, other than understanding when they should be in our territory, I now also rely on the color of their bill. The American Tree Sparrow (Above, 1-10-10, in my front yard) has a bicolored bill, dark upper mandible and yellowish lower mandible, which is barely visible in the photo above. One of my goals this coming winter is to try to get a better photo of this guy.
The Field Sparrow’s bill is all one pinkish color (Below top, 6-26-10).

Field Sparrow hanging around in ... what else? ... a field; Blackhawk Springs Forest Preserve; 6-26-10.

Field Sparrow singing away in Rock Cut State Park; 5-23-10.