Larus argentatus
Webbed triangles running everywhere along the tide line.
2.5–3 in long. Three webbed forward toes. Small rear toe sometimes shows as a dot. Meandering trail across wet sand. Dropped shells cracked on rocks nearby.
Beaches, harbors, landfills, lakes. North Atlantic and Great Lakes, widespread in winter.
Diurnal
Fish, crabs, eggs, scraps
Gulls drum their feet on wet sand to trick worms into surfacing.
Should I be concerned?
Harmless, though bold around food.