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The loons (North America) or divers (UK/Ireland) are a group of aquatic birds found in many parts of North America and northern Eurasia. All living species of loons are members of the genus ''Gavia'', family Gaviidae and order Gaviiformes. ==Description== The loon, the size of a large duck or small goose, resembles these birds in shape when swimming. Like ducks and geese but unlike coots (which are Rallidae) and grebes (Podicipedidae), the loon's toes are connected by webbing. The bird may be confused with cormorants (Phalacrocoracidae), which are not too distant relatives of divers and like them are heavy set birds whose bellies – unlike those of ducks and geese – are submerged when swimming. Flying loons resemble a plump goose with a seagull's wings, relatively small in proportion to the bulky body. The bird holds its head pointing slightly upwards during swimming, but less so than cormorants do. In flight the head droops more than in similar aquatic birds. Archibald Thorburn Plate 77.jpg|1918 illustration of a variety of divers by Archibald Thorburn. Top: great northern loon, Mid-left: red-throated loon, Mid-right: yellow-billed loon, Bottom: black-throated loon Gavia immer -Marshfield, Vermont, USA -flying-8 (5).jpg|Great northern loon flying exhibiting the typical flight profile of a ''Gavia'' species Plongeon imbrin ailes.jpg|Great northern loon (''G. immer'') rearing up. Note the plump body and pointed but rather short wings Yellow-billed Loon.jpg|White-billed diver or yellow-billed loon (''Gavia adamsii'') in winter plumage Male and female loons have identical plumage. Plumage is largely patterned black-and-white in summer, with grey on the head and neck in some species. All have a white belly. This resembles many sea-ducks (Merginae) – notably the smaller goldeneyes (''Bucephala'') – but is distinct from most cormorants which rarely have white feathers, and if so usually as large rounded patches rather than delicate patterns. All species of divers have a spear-shaped bill. Males are larger on average, but relative size is only apparent when the male and female are together. In winter plumage is dark grey above, with some indistinct lighter mottling on the wings, and a white chin, throat and underside. The species can then be distinguished by certain features, such as size and colour of head, neck, back and bill, but often reliable identification of wintering divers is difficult even for experts – particularly as the smaller immature birds look similar to winter-plumage adults, making size an unreliable means of identification.〔 〕 Gaviiformes are among the few groups of birds in which the young moult into a second coat of down feathers after shedding the first one, rather than growing juvenile feathers with downy tips that wear off as is typical in many birds. This trait is also found in tubenoses (Procellariiformes) and penguins (Sphenisciformes), both relatives of the loons.〔Olson (1985: p. 212)〕 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「Loon」の詳細全文を読む スポンサード リンク
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