"Bonxie" redirects here. For the Stornoway album, seeBonxie (album).
This article is about the skua which breeds in the northeast Atlantic and winters in the north Atlantic. For the southern great skua, which is distributed in theSouthern Ocean, seeBrown skua.
Thegreat skua (Stercorarius skua), sometimes known by the namebonxie in Britain, is a largeseabird in the skua familyStercorariidae. It is roughly the size of aherring gull. It mainly eats fish caught at the sea surface or taken from other birds.
The great skua wasdescribed from theFaroe Islands andIceland by the Danish zoologistMorten Thrane Brünnich in 1764 under thebinomial nameCatharacta skua.[2][3] It is now placed in thegenusStercorarius that was introduced by the French zoologistMathurin Jacques Brisson in 1760.[4][5] The English name and species name "skua" is believed to originate from the Faroeseskúvur orskúgvur[ˈskɪkvʊər] and is the only known bird name to originate from theFaroes that has come into regular use elsewhere.[6][7] In Britain, it is sometimes known by the namebonxie, aShetland name ofNorse origin.[8][9] The genus nameStercorarius isLatin and means "of dung"; the food disgorged by other birds when pursued by skuas was once thought to be excrement.[10] The species ismonotypic: nosubspecies are recognised.[5]
Great skuas measure 50–58 cm (20–23 in) long and have a 125–140 cm (49–55 in)wingspan. One study found that 112 males weighed an average of 1.27 kg (2 lb 13 oz) and that 125 females weighed an average of 1.41 kg (3 lb 2 oz).[11] Adults are a streaked greyish brown, with a black cap, while juveniles are a warmer brown and unstreaked below. They have a short, blunt tail, and a powerful flight. The great skua's call is a harshhah-hah-hah-hah; quacking and croaking noises have also been heard. Distinguishing this skua from the other North Atlantic skuas (parasitic jaeger,pomarine jaeger andlong-tailed jaeger) is relatively straightforward. Theherring gull size, massive barrel chest and white wing flashes of this bird are distinctive even at a distance. It is sometimes said to give the impression of acommon buzzard. Identification of this skua is only complicated when it is necessary to distinguish it from the closely related large southern-hemisphere skuas. Despite its name, the great skua is marginally smaller on average than the other 3 large southern-hemisphere skuas, although not by enough to distinguish them by size in the field.[11] Some authorities still regard the great skua as conspecific with some of these southern skuas, and as a group they have sometimes been separated in the genusCatharacta, although currently this taxonomy is not commonly followed.
Great skua, as another pair flew too close to their nest site (Shetland)
Genetic studies have found surprising similarities between the great skua and the pomarine skua, despite their dissimilar appearance. Many ornithologists now believe either that the great skua originated as a hybrid between the pomarine skua and one of the southern-hemisphere species,[12] presumably as a result of vagrancy or migration across the equator by the southern species, or that the pomarine skua evolved from hybridization of the great skua and one of the small Arctic species (seepomarine jaeger for details).
The great skua breeds inIceland,Norway, theFaroe Islands, and onScottish islands, with some individuals breeding on mainland Scotland and in the northwest ofIreland. They breed on coastal moorland and rocky islands, usually laying two spotted olive-brown eggs in grass-lined nests. Like other skuas, they will fly at the head of a human or other intruder approaching their nest. Although it cannot inflict serious damage, such an experience with a bird of this size is frightening. They are amigrant species, wintering at sea in theAtlantic Ocean and regularly reachingNorth American waters. They are vagrant to Mediterranean countries (e.g. Turkey).
They eat mainly fish, birds,eggs, carrion, offal,rodents, rabbits, and occasionally berries. They have been known to prey on lambs, and even pony foals. Probably their most prolific food source is by-catch abandoned by fishing vessels.[13]
They will often obtain fish by robbinggulls,terns and evennorthern gannets of their catches. They will also directly attack and kill other seabirds, up to the size of herring gulls. Like most other skuaspecies, it continues thispiratical 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. Due to its size, aggressive nature and fierce defence of its nest, the great skua has little to fear from other predators. Whilefledglings can fall prey torats,cats or theArctic fox, healthy adults are threatened only by greater raptors such as thegolden eagle, thewhite-tailed eagle, and more rarely, at sea by theorca.
An aerialapex predator, the great skua is an also an aggressivekleptoparasite, deliberately harassing birds as large as gannets to steal a free meal. It also readily kills and eats smaller birds such aspuffins. Great skuas show little to no fear of humans – anybody getting close to the nest will be repeatedly dive-bombed by the territorial adults.Unusual behaviour bySt Kilda's skuas was recorded in 2007 during research into recent falls in theLeach's storm petrel population. Using night vision gear, ecologists observed the skuas preying on the petrels at night, a remarkable strategy for a seabird.[14]
^Brisson, Mathurin Jacques (1760).Ornithologie, ou, Méthode Contenant la Division des Oiseaux en Ordres, Sections, Genres, Especes & leurs Variétés (in French and Latin). Paris: Jean-Baptiste Bauche.Vol. 1, p. 56,Vol. 6, p. 149.
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