About Larus hyperboreus Gunnerus, 1767
This is the glaucous gull, scientifically named Larus hyperboreus Gunnerus, 1767. It is a large, powerful gull, the second-largest of all gull species, and is very pale in every plumage stage, with no black markings on either its wings or tail. Adult glaucous gulls are pale grey on their upper bodies, with a thick yellow bill. Juveniles are very pale grey, with a pink and black bill. This species is considerably larger, bulkier, and has a thicker bill than the similar-looking Iceland gull, and can sometimes reach the same size as the great black-backed gull, which is often named the largest gull species. In some areas, glaucous gulls are about the same weight as great black-backed gulls, or even heavier, and the species has a greater maximum weight than the great black-backed gull. Glaucous gulls weigh between 960 and 2,700 g (2.12 to 5.95 lb). Historically, average weights have been reported as 1.55 kg (3.4 lb) for males and 1.35 kg (3.0 lb) for females. At a breeding colony on Coats Island, Canada, glaucous gulls are nearly 15% heavier than other recorded populations. This colony has a mean weight of 1.86 kg (4.1 lb) for five males and 1.49 kg (3.3 lb) for seven females. Another study reported even higher weights for glaucous gulls on Wrangel Island: 9 males reportedly averaged 2.32 kg (5.1 lb), and six females averaged 2.1 kg (4.6 lb). If these measurements are accurate, the glaucous gull would be the heaviest gull and shorebird in the world, though it is not known to be the largest in average length. Glaucous gulls measure 55 to 77 cm (22 to 30 in) in total length, with a wingspan of 132 to 170 cm (52 to 67 in); some individual specimens may reach a wingspan of 182 cm (72 in). Standard measurements for the species are: wing chord 40.8 to 50.1 cm (16.1 to 19.7 in), bill length 4.9 to 6.9 cm (1.9 to 2.7 in), and tarsus length 6 to 7.7 cm (2.4 to 3.0 in). Glaucous gulls take four years to reach full maturity. Their call is a "laughing" cry similar to that of the herring gull, but deeper in pitch. Glaucous gulls breed in Arctic regions of the Northern Hemisphere, and migrate south to winter on shores of the Holarctic. They winter across the North Atlantic and North Pacific Oceans, reaching as far south as the British Isles and the northernmost states of the United States, and also winter on the Great Lakes. A small number of individuals sometimes reach the southern United States and northern Mexico. This seagull species breeds either in colonies or as single pairs on coasts and cliffs, building a lined nest on the ground or cliff face. Typically, females lay two to four light brown eggs marked with dark brown splotches. Like most Larus gulls, glaucous gulls are omnivores. Their diet includes fish, insects, molluscs, starfish, offal, scraps, eggs, small birds, small mammals, carrion, as well as seeds, berries, and grains.
