Great Skua
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| Great Skua | ||||||||||||||
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| Stercorarius skua Brunnich,, 1764 |
The Great Skua, Stercorarius skua, is a large seabird in the skua family Stercorariidae. In Scotland, it is also known by the name Bonxie, a name which originates from the Shetland name for a bully.
This is a large skua 50-58cm in length with a 125-140cm wingspan. It breeds in Iceland, Norway, the Faroe Islands and the Scottish islands. It nests on coastal moorland and rocky islands, laying usually two eggs. Like other skuas, it will fly at the head of a human or other intruder approaching its nest. Although it cannot inflict serious damage, it is a frightening and painful experience with a bird of this size. It is a migrant, wintering at sea in the Atlantic Ocean.
This bird eats mainly fish, which it often obtains by robbing gulls, terns and even Gannets of their catches. It will also directly attack and kill other seabirds, up to the size of Great Black-backed Gulls. Like most other skua species, it continues this piratical behaviour throughout the year, showing less agility and more brute force than the smaller skuas when it harasses its victims. A common technique is to fly up to a Gannet in mid-air and grab it by the wing, so that it stalls and falls into the sea, where the Great Skua then physically attacks it until it surrenders its catch.
Distinguishing this skua from the other North Atlantic skuas (Arctic Skua, Pomarine Skua and Long-tailed Skua) is relatively straightforward. The Herring Gull size, massive barrel chest and white wing flashes of this bird are distinctive even at a distance. It is sometimes said to give a Buzzard-like impression. Adults are streaked greyish brown, with a black cap, juveniles are a warmer brown and unstreaked below. The flight is direct and powerful.
Identification of this skua is only complicated when it is necessary to distinguish it from the closely-related large southern hemisphere skuas.
Genetic studies have found surprising similarities between the Great Skua and the Pomarine Skua, despite their dissimilar appearance. Many ornithologists now believe that the Great Skua originated as a hybrid between the Pomarine Skua and one of the southern-hemisphere species, presumably as a result of vagrancy or migration across the equator by the southern species.nl:Grote jager