I would appreciate some help with a problem gull that has been nagging at the back of my mind.
The attached photos were taken at Port Mahon, Delaware Bay, Delaware State, USA in June 2004. They show a large dark backed gull. At the time it was sufficiently different for me to take photos but I was unsure what it was and eventually just decided it was a runt GBBG. However, recent discussion and postings concerning Slaty-backed Gull have made me question it more. The combination of upper part colour, large white tertial edging, deep pink legs and size and structure (smaller and more compact that GBBG) all seem consistent with S-b Gull, but I have no personal experience of this species and I would appreciate any feedback from anyone who does have experience. Its certainly not like any other GBBG that I have seen before or since.