This slide arrived labeled as a Thayer's
Gull (Larus thayeri) - crossed out and relabeled
as "IC?", photographed by Tony Leukering at Tullytown
Landfill, Penn. on 24th December 1991. It seems to me that this
could possibly be an extreme dark ICGU, extreme lightly-marked
THGU, a "Thayer's-type" argentatus HEGU, or an
extreme lightly-marked smithsonianus HEGU; any comments
on this bird?