Like most Larus gulls, these are omnivores, eating fish, molluscs, offal, scraps, and eggs.

They forage while flying, picking up food at or just below the water's surface, and they also feed while walking or swimming.

Their scavenging habits lead them to frequent garbage dumps, sewage outlets, and places where fish are cleaned.

The American taxon of Iceland gull by the American Ornithological Society as of 2017 considers the following as subspecies:[6] The nominate subspecies, L. g. glaucoides, is very pale in all plumage, with absolutely no melanin in the tips of the primaries in adult plumage.

Immatures are very pale grey; the bill is more extensively dark than with glaucous gull, and lacks pink.