|
Gannets are seabirds comprising the genus ''Morus'', in the family Sulidae, closely related to boobies. They have a maximum lifespan of up to 35 years.〔https://www.seabird.org/wildlife/seabirds/gannet/12/26/47〕 The gannets are large white birds with yellowish heads; black-tipped wings; and long bills. Northern gannets are the largest seabirds in the North Atlantic, with a wingspan of up to . The other two species occur in the temperate seas around southern Africa, southern Australia and New Zealand. Gannets hunt fish by diving from a height into the sea and pursuing their prey underwater. Gannets have a number of adaptations which enable them to do this: * no external nostrils, they are located inside the mouth instead; * air sacs in the face and chest under the skin which act like bubble wrapping, cushioning the impact with the water; * positioning of the eyes far enough forward on the face for binocular vision, allowing them to judge distances accurately. Gannets can dive from a height of , achieving speeds of as they strike the water, enabling them to catch fish much deeper than most airborne birds. The gannet's supposed capacity for eating large quantities of fish has led to "gannet" becoming a disapproving description of somebody who eats excessively, similar to "glutton". ==Mating and nesting== Gannets are colonial breeders on islands and coasts, normally laying one chalky, blue egg. It takes five years for gannets to reach maturity. First-year birds are completely black, and subsequent sub-adult plumages show increasing amounts of white. The most important nesting ground for northern gannets is the United Kingdom with about two thirds of the world's population. These live mainly in Scotland, including the Shetland Isles. The rest of the world's population is divided between Canada, Ireland, Faroe Islands and Iceland, with small numbers in France (they are often seen in the Bay of Biscay), the Channel Islands, Norway and a single colony in Germany on Heligoland. The biggest northern gannet colony is in the Scottish islands of St Kilda; this colony alone comprises 20% of the entire world's population. Sulasgeir off the coast of the Isle of Lewis, Bass Rock in the Firth of Forth, Grassholm in Pembrokeshire, Sceilig Bheag, Ireland and Bonaventure Island, Quebec are also important northern gannet breeding sites. 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「Gannet」の詳細全文を読む スポンサード リンク
|