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The great skua (''Stercorarius skua''), sometimes known by the name bonxie in Britain, is a large
seabird Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same enviro ...
in the skua family Stercorariidae. It is roughly the size of a
herring gull Herring gull is a common name for several birds in the genus '' Larus'', all formerly treated as a single species. Three species are still combined in some taxonomies: * American herring gull (''Larus smithsonianus'') - North America * European ...
. It mainly eats fish caught at the sea surface or taken from other birds.


Taxonomy

The great skua was described from the
Faroe Islands The Faroe Islands ( ), or simply the Faroes ( fo, Føroyar ; da, Færøerne ), are a North Atlantic island group and an autonomous territory of the Kingdom of Denmark. They are located north-northwest of Scotland, and about halfway bet ...
and
Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...
by the Danish zoologist
Morten Thrane Brünnich Morten Thrane Brünnich (30 September 1737 – 19 September 1827) was a Danish zoologist and mineralogist. Biography Brünnich was born in Copenhagen, the son of a portrait painter. He studied oriental languages and theology, but soon became ...
in 1764 under the binomial name ''Catharacta skua''. It is now placed in the
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
'' Stercorarius'' that was introduced by the French zoologist
Mathurin Jacques Brisson Mathurin Jacques Brisson (; 30 April 1723 – 23 June 1806) was a French zoologist and natural philosopher. Brisson was born at Fontenay-le-Comte. The earlier part of his life was spent in the pursuit of natural history; his published works ...
in 1760. The English name and species name "skua" is believed to originate from the Faroese ''skúvur'' or ''skúgvur'' and is the only known bird name to originate from the
Faroes The Faroe Islands ( ), or simply the Faroes ( fo, Føroyar ; da, Færøerne ), are a North Atlantic island group and an autonomous territory of the Kingdom of Denmark. They are located north-northwest of Scotland, and about halfway betw ...
that has come into regular use elsewhere. In Britain, it is sometimes known by the name bonxie, a Shetland name of Norse origin. The genus name ''Stercorarius'' is
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
and means "of dung"; the food disgorged by other birds when pursued by skuas was once thought to be excrement. The species is
monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...
: no subspecies are recognised.


Description

Great skuas measure long and have a
wingspan The wingspan (or just span) of a bird or an airplane is the distance from one wingtip to the other wingtip. For example, the Boeing 777–200 has a wingspan of , and a wandering albatross (''Diomedea exulans'') caught in 1965 had a wingspan o ...
. One study found that 112 males weighed an average of and that 125 females weighed an average of . 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 harsh ''hah-hah-hah-hah''; quacking and croaking noises have also been heard. Distinguishing this skua from the other North Atlantic skuas (
parasitic jaeger The parasitic jaeger (''Stercorarius parasiticus''), also known as the Arctic skua, Arctic jaeger or parasitic skua, is a seabird in the skua family Stercorariidae. It is a migratory species that breeds in Northern Scandinavia, Scotland, Iceland, ...
,
pomarine jaeger The pomarine jaeger (''Stercorarius pomarinus''), pomarine skua, or pomatorhine skua, is a seabird in the skua family Stercorariidae. It is a migrant, wintering at sea in the tropical oceans. Taxonomy Its relationships are not fully resolved; i ...
and
long-tailed jaeger The long-tailed skua or long-tailed jaeger (''Stercorarius longicaudus'') is a seabird in the skua family Stercorariidae. Etymology The word "jaeger" is derived from the German word ''Jäger'', meaning "hunter". The English word "skua" comes fr ...
) is relatively straightforward. The
herring gull Herring gull is a common name for several birds in the genus '' Larus'', all formerly treated as a single species. Three species are still combined in some taxonomies: * American herring gull (''Larus smithsonianus'') - North America * European ...
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 a common 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. 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 genus ''Catharacta'', although currently this taxonomy is not commonly followed.


Origins

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, 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 (see
pomarine jaeger The pomarine jaeger (''Stercorarius pomarinus''), pomarine skua, or pomatorhine skua, is a seabird in the skua family Stercorariidae. It is a migrant, wintering at sea in the tropical oceans. Taxonomy Its relationships are not fully resolved; i ...
for details).


Breeding

The great skua breeds in
Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...
,
Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and the ...
, the
Faroe Islands The Faroe Islands ( ), or simply the Faroes ( fo, Føroyar ; da, Færøerne ), are a North Atlantic island group and an autonomous territory of the Kingdom of Denmark. They are located north-northwest of Scotland, and about halfway bet ...
, and on Scottish islands, with some individuals breeding on mainland Scotland and in the northwest of
Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...
. 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 a migrant species, wintering at sea in the
Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...
and regularly reaching North American waters. They are vagrant to Mediterranean countries (e.g. Turkey).


Diet

They eat mainly fish, birds,
egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
s, carrion, offal,
rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...
s, 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. They will often obtain fish by robbing
gull Gulls, or colloquially seagulls, are seabirds of the family Laridae in the suborder Lari. They are most closely related to the terns and skimmers and only distantly related to auks, and even more distantly to waders. Until the 21st century ...
s,
tern Terns are seabirds in the family Laridae that have a worldwide distribution and are normally found near the sea, rivers, or wetlands. Terns are treated as a subgroup of the family Laridae which includes gulls and skimmers and consists of e ...
s and even
northern gannet The northern gannet (''Morus bassanus'') is a seabird, the largest species of the gannet family, Sulidae. It is native to the coasts of the Atlantic Ocean, breeding in Western Europe and Northeastern North America. It is the largest seabird in t ...
s of their catches. They will also directly attack and kill other seabirds, up to the size of herring gulls. Like most other skua
species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
, 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. Due to its size, aggressive nature and fierce defence of its nest, the great skua has little to fear from other predators. While fledglings can fall prey to rats,
cat The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...
s or the
Arctic fox The Arctic fox (''Vulpes lagopus''), also known as the white fox, polar fox, or snow fox, is a small fox native to the Arctic regions of the Northern Hemisphere and common throughout the Arctic tundra biome. It is well adapted to living in ...
, healthy adults are threatened only by greater raptors such as the
golden eagle The golden eagle (''Aquila chrysaetos'') is a bird of prey living in the Northern Hemisphere. It is the most widely distributed species of eagle. Like all eagles, it belongs to the family Accipitridae. They are one of the best-known birds of ...
, the
white-tailed eagle The white-tailed eagle (''Haliaeetus albicilla'') is a very large species of sea eagle widely distributed across temperate Eurasia. Like all eagles, it is a member of the family Accipitridae (or accipitrids) which includes other diurnal raptors ...
, and more rarely, by the
orca The orca or killer whale (''Orcinus orca'') is a toothed whale belonging to the oceanic dolphin family, of which it is the largest member. It is the only extant species in the genus '' Orcinus'' and is recognizable by its black-and-white ...
.


Predation account

An aerial
apex predator An apex predator, also known as a top predator, is a predator at the top of a food chain, without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the highest trophic lev ...
, the great skua is an aggressive pirate of the seas, deliberately harassing birds as large as gannets to steal a free meal. It also readily kills and eats smaller birds such as
puffins Puffins are any of three species of small alcids (auks) in the bird genus ''Fratercula''. These are pelagic seabirds that feed primarily by diving in the water. They breed in large colonies on coastal cliffs or offshore islands, nesting in crev ...
. Great skuas show little to no fear of humans – anybody getting close to the nest will be repeatedly dive-bombed by the angry adults. Unusual behaviour by St Kilda's skuas was recorded in 2007 during research into recent falls in the Leach's storm petrel population. Using night vision gear, ecologists observed the skuas preying on the petrels at night, a remarkable strategy for a seabird.


Gallery

File:GreatSkuaInWater.jpg, Great skua in water File:Skua_Runde.jpg, At the Norwegian bird island Runde File:Skua_Runde2.jpg, At Runde File:Skua.jpg, In flight. File:Great skua (Stercorarius skua), Hallig Hooge.jpg, Great skua at North Sea island Hallig Hooge / Germany File:Große Raubmöwe (Stercorarius skua) auf Handa Island.JPG, At
Handa Island Handa Island ( gd, Eilean Shannda) or simply Handa is an island off the west coast of Sutherland, Scotland. It is and at its highest point. The island is of national importance for its birdlife and maritime vegetation, and is a Scottish W ...
/ Scotland Stercorarius skua MHNT.ZOO.2010.11.139.8.jpg , Museum specimen


References

*


External links


More great skua information and photos
at the Handa Island Skua Project * * * * * * * * {{Taxonbar, from=Q207760
great skua The great skua (''Stercorarius skua''), sometimes known by the name bonxie in Britain, is a large seabird in the skua family Stercorariidae. It is roughly the size of a herring gull. It mainly eats fish caught at the sea surface or taken fr ...
Birds of the Arctic Birds of Iceland Birds of Scandinavia Birds of the Atlantic Ocean
great skua The great skua (''Stercorarius skua''), sometimes known by the name bonxie in Britain, is a large seabird in the skua family Stercorariidae. It is roughly the size of a herring gull. It mainly eats fish caught at the sea surface or taken fr ...
Taxa named by Morten Thrane Brünnich Taxobox binomials not recognized by IUCN Apex predators