Lake County, IL; 04 January 2016.
Here's a bird I've not personally seen anything similar to before:
The almost solidly filled black upperwing, including the tertials, seems a bit too much for a pure American Herring. The legs are noticeably short and the wing projection longer than usual for Herring. The head streaking on the back of the head is reminiscent of LBBG. The bill - proportionately small and matching the smaller body size - is still mostly black (not very typical in 2nd winter HERGs, but also not unheard of). The gray scaps were a tad darker than I see on 2nd basic Herrings, but this very well may be due to brown tones blended in these feathers.
To cut to the chase, I do wonder if this can be a HERG x LBBG or a backcross of some sort. Where to put this one? Dark HERG?