Photographed in mid August on the James Bay Coast of Ontario, Canada. The bird struck us as very odd (single flyby while seawatching), in a location where summering sub-adult gulls were unusual. (Possibly the only first alternate large gull we saw in 2 weeks of watching).
Map of location, along with the only photos of the bird here:
Sorry for the bad photos of such an ugly bird! But I thought I would put them out for fun.