Most likely a juvenile Song sparrow.
Perhaps a Vesper sparrow (slight eye ring) and there
may be a considerable variation in the amount of
streaking on breast. I have a shot of just such a plain-
looking sparrow. I wasn't quite sure about it and I
can't seem to locate it now. I did find a shot of a Savannah
sparrow from a field in the Rouge. The quality of that
field was ruined by the zoo because they wanted extra
parking. Ultimately, the destruction of that ecosystem
was all for nothing because I've never seen any parking
on that field. Needless to say, once the wet sphagnum
moss was excavated the Savannah sparrows never
returned.