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The glaucous gull (''Larus hyperboreus'') is a large gull which breeds in the Arctic regions of the Northern Hemisphere and the Atlantic coasts of Europe. It is migratory, wintering from in the North Atlantic and North Pacific oceans as far south as the British Isles and northernmost states of the USA, also on the Great Lakes. A few birds sometimes reach the southern USA and northern Mexico. There are four subspecies: *''L. h. hyperboreus'', (Gunnerus, 1767): northern Europe to north-western Siberia *''L. h. pallidissimus'', (Portenko, 1939): north-western Siberia to the Bering Sea *''L. h. barrovianus'', (Ridgway, 1886): Alaska to north-west Canada *''L. h. leuceretes'', (Schleep, 1819): north-central Canada to Greenland and Iceland This species breeds colonially or singly on coasts and cliffs, making a lined nest on the ground or cliff. Normally, 2–4 light brown eggs with dark chocolate splotches are laid. This is a large and powerful gull, very pale in all plumages, with no black on either of the wings or the tail. The term ''glaucous'' describes its colouration. Adults are pale grey above, with a thick yellow bill. Immatures are very pale grey with a pink and black bill. This species is considerably larger, bulkier and thicker-billed than the similar Iceland gull, and can sometimes equal the size of the great black-backed gull, the largest gull species. They can weigh anywhere from , averaging in males and in females. At the colony on Coats Island in Canada, the gulls are nearly 15% heavier than other known populations, with a mean weight in males and . Thus, Coats Island glaucous gulls are about the same weight as great black-backed gulls or even marginally heavier and their maximum weight is greater.〔''CRC Handbook of Avian Body Masses, 2nd Edition'' by John B. Dunning Jr. (Editor). CRC Press (2008), ISBN 978-1-4200-6444-5.〕 These gulls range from in length and can span across the wings.〔〔 (2011)〕 Among standard measurements, the wing chord is , the bill is and the tarsus is .〔 They take four years to reach maturity. The call is a "laughing" cry similar to that of the herring gull but deeper. These are omnivores like most ''Larus'' gulls, and they will eat fish, insects, molluscs, starfish, offal, scraps, eggs, small birds, small mammals and carrion as well as seeds, berries and grains. ==References== * * 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「glaucous gull」の詳細全文を読む スポンサード リンク
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