I swung by the New Buffalo area a couple days ago. While quickly scanning through the gulls in the howling wind I fairly quickly picked up the hybrid dark-mantled gull that's been kicked around as a Chandeleur Gull, Great Black-back x Herring, or who knows what.
We haven't seen it at Tiscornia this year and thought he might have joined Hughie. He hadn't.
There's always some semi-odd gulls in the New Buffalo flock (though with 300 Herring Gulls, simple probability says that 1% of them will be outliers). This first fall bird (no longer a juvie with first winter back plumage) is a lot more white-headed than the average first year HEGU.
If this bird was on the other side of Lake Michigan I bet a whole bunch of people would be desperately gripping for a Euro Herring Gull, especially if you compare it to a recently arrived juvenile Herring Gull in fresh dark plumage presumably from the high arctic.