Great Skua
Encyclopedia
The Great Skua, Stercorarius skua, is a large seabird
in the skua
family Stercorariidae. In Britain, it is sometimes known by the name Bonxie, a Shetland name of unknown origin.
. The adult is streaked greyish brown, with a black cap, while the juvenile is a warmer brown and unstreaked below. Its tail is short and blunt. The flight is direct and powerful. The Brown 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 (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 the impression of a Common Buzzard
(which in America would be called a hawk). Identification of this skua is only complicated when it is necessary to distinguish it from the closely related large southern-hemisphere skuas. 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 is not commonly followed.
for details).
, Norway
, the Faroe Islands
and the Scottish
islands, with a few on mainland Scotland. It breeds on coastal moorland and rocky islands, usually laying two spotted olive-brown eggs in grass-lined nests. Like other skuas, it will fly at the head of a human or other intruder approaching its nest. Although it cannot inflict serious damage, such an experience with a bird of this size is frightening. It is a migrant
, wintering at sea in the Atlantic Ocean
and regularly reaching North America
n waters. Vagrant to Mediterranean countries (e.g. Turkey).
eats mainly fish, which it often obtains by robbing gull
s, tern
s and even Northern Gannet
s of their catches. It will also directly attack and kill other seabirds, up to the size of Great Black-backed Gull
s. 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. It also eats small mammals, eggs, berries and carrion. Due to its size, aggressive nature and fierce defence of its nest, the Great Skua has hardly anything to fear from other predators. While fledgling
s can fall prey to rat
s, cat
s or the Arctic Fox
, healthy adults are only threatened by the Golden Eagle
and the White-tailed Eagle
.
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.
Seabird
Seabirds are birds that have 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 environmental problems and feeding niches have resulted in similar adaptations...
in the skua
Skua
The skuas are a group of seabirds with about seven species forming the family Stercorariidae and the genus Stercorarius. The three smaller skuas are called jaegers in North America....
family Stercorariidae. In Britain, it is sometimes known by the name Bonxie, a Shetland name of unknown origin.
Description
This is a large skua, measuring 50 – in length with a 125 – wingspanWingspan
The wingspan of an airplane or a bird, is the distance from one wingtip to the other wingtip. For example, the Boeing 777 has a wingspan of about ; and a Wandering Albatross caught in 1965 had a wingspan of , the official record for a living bird.The term wingspan, more technically extent, is...
. The adult is streaked greyish brown, with a black cap, while the juvenile is a warmer brown and unstreaked below. Its tail is short and blunt. The flight is direct and powerful. The Brown 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 (Arctic Skua
Arctic Skua
The Parasitic Jaeger, also known as the Arctic Skua or Parasitic Skua, is a seabird in the skua family Stercorariidae....
, Pomarine Skua
Pomarine Skua
The Pomarine Skua, Stercorarius pomarinus, known as Pomarine Jaeger in North America, is a seabird in the skua family Stercorariidae. It is a migrant, wintering at sea in the tropical oceans.- Taxonomy :...
and Long-tailed Skua
Long-tailed Skua
The Long-tailed Skua, Stercorarius longicaudus is a seabird in the skua family Stercorariidae....
) is relatively straightforward. The Herring Gull
Herring Gull
The European Herring Gull is a large gull , and is the most abundant and best known of all gulls along the shores of western Europe. It breeds across Northern Europe, Western Europe, Scandinavia and the Baltic states...
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
Common Buzzard
The Common Buzzard is a medium to large bird of prey, whose range covers most of Europe and extends into Asia. It is usually resident all year, except in the coldest parts of its range, and in the case of one subspecies.-Description:...
(which in America would be called a hawk). Identification of this skua is only complicated when it is necessary to distinguish it from the closely related large southern-hemisphere skuas. 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 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 [Furness and Hamer, 2003], 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 SkuaPomarine Skua
The Pomarine Skua, Stercorarius pomarinus, known as Pomarine Jaeger in North America, is a seabird in the skua family Stercorariidae. It is a migrant, wintering at sea in the tropical oceans.- Taxonomy :...
for details).
Breeding
The Great Skua breeds in IcelandIceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
, Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
, the Faroe Islands
Faroe Islands
The Faroe Islands are an island group situated between the Norwegian Sea and the North Atlantic Ocean, approximately halfway between Scotland and Iceland. The Faroe Islands are a self-governing territory within the Kingdom of Denmark, along with Denmark proper and Greenland...
and the Scottish
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
islands, with a few on mainland Scotland. It breeds on coastal moorland and rocky islands, usually laying two spotted olive-brown eggs in grass-lined nests. Like other skuas, it will fly at the head of a human or other intruder approaching its nest. Although it cannot inflict serious damage, such an experience with a bird of this size is frightening. It is a migrant
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
, wintering at sea in the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
and regularly reaching North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
n waters. Vagrant to Mediterranean countries (e.g. Turkey).
Diet
This birdBird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
eats mainly fish, which it often obtains by robbing gull
Gull
Gulls are birds in the family Laridae. They are most closely related to the terns and only distantly related to auks, skimmers, and more distantly to the waders...
s, tern
Tern
Terns are seabirds in the family Sternidae, previously considered a subfamily of the gull family Laridae . They form a lineage with the gulls and skimmers which in turn is related to skuas and auks...
s and even Northern Gannet
Northern Gannet
The Northern Gannet is a seabird and is the largest member of the gannet family, Sulidae.- Description :Young birds are dark brown in their first year, and gradually acquire more white in subsequent seasons until they reach maturity after five years.Adults are long, weigh and have a wingspan...
s of their catches. It will also directly attack and kill other seabirds, up to the size of Great Black-backed Gull
Great Black-backed Gull
The Great Black-backed Gull is the largest gull in the world, which breeds on the European and North American coasts and islands of the North Atlantic...
s. Like most other skua species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, it continues this piratical behaviour
Kleptoparasitism
Kleptoparasitism or cleptoparasitism is a form of feeding in which one animal takes prey or other food from another that has caught, collected, or otherwise prepared the food, including stored food...
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. It also eats small mammals, eggs, berries and carrion. Due to its size, aggressive nature and fierce defence of its nest, the Great Skua has hardly anything to fear from other predators. While fledgling
Fledgling
Fledgling or Fledglings may refer to:* Curtiss Fledgling, a trainer aircraft* Fergie's Fledglings, a group of Manchester United players recruited under the management of Alex Ferguson...
s can fall prey to rat
Rat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...
s, cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
s or the Arctic Fox
Arctic fox
The arctic fox , also known as the white fox, polar fox or snow fox, is a small fox native to Arctic regions of the Northern Hemisphere and is common throughout the Arctic tundra biome. The Greek word alopex, means a fox and Vulpes is the Latin version...
, healthy adults are only threatened by the Golden Eagle
Golden Eagle
The Golden Eagle is one of the best known birds of prey in the Northern Hemisphere. Like all eagles, it belongs to the family Accipitridae. Once widespread across the Holarctic, it has disappeared from many of the more heavily populated areas...
and the White-tailed Eagle
White-tailed Eagle
The White-tailed Eagle , also known as the Sea Eagle, Erne , or White-tailed Sea-eagle, is a large bird of prey in the family Accipitridae which includes other raptors such as hawks, kites, and harriers...
.
Predation account
Unusual behaviour by St Kilda'sSt Kilda, Scotland
St Kilda is an isolated archipelago west-northwest of North Uist in the North Atlantic Ocean. It contains the westernmost islands of the Outer Hebrides of Scotland. The largest island is Hirta, whose sea cliffs are the highest in the United Kingdom and three other islands , were also used for...
Skuas was recorded in 2007 during research into recent falls in the Leach's Storm-petrel
Leach's Storm-petrel
The Leach's Storm Petrel or Leach's Petrel is a small seabird of the tubenose family. It is named after the British zoologist William Elford Leach....
population. Using night vision gear, ecologists observed the skuas preying on the petrels at night, a remarkable strategy for a seabird.
External links
- More Great Skua information and photos at the Handa Island Skua Project
- Great Skua videos, photos & sounds on the Internet Bird Collection