Skua
Encyclopedia
The skuas are a group of seabird
s with about seven species forming the family
Stercorariidae and the genus
Stercorarius. The three smaller skuas are called jaegers in North America.
The English word "skua" comes from the Faroese
name skúgvur ˈskɪkvʊər for the Great Skua
, with the island of Skúvoy
renowned for its colony of that bird. The general Faroese term for skuas is kjógvi ˈtʃɛkvə. The word "jaeger" is derived from the German
word Jäger, meaning "hunter".
Skuas nest on the ground in temperate and Arctic regions, and are long-distance migrants
. They have even been sighted at the South Pole
.
, and carrion
. Many are partial kleptoparasites
, comprising up to 95% of the feeding methods of wintering birds, by chasing gulls, terns and other seabirds to steal their catches, regardless of the size of the species attacked (up to 3 times heavier than the attacking skua). The larger species, such as the Great Skua
, also regularly kill and eat adult birds, such as puffin
s and gull
s, and have been recorded as killing birds as large as a Grey Heron
. On the breeding grounds they commonly eat lemming
s, and the eggs and young of other birds. In the Southern oceans and Antarctica region, some skua species (especially the South Polar Skua
) will readily scavenge the carcasses at breeding colonies of penguin
s and pinniped
s, sometimes taking live penguin chicks. In these areas, skuas seem to defer to the considerably larger giant petrel
s.
They are medium to large bird
s, typically with grey or brown plumage, often with white markings on the wings. The skuas range in size from the Long-tailed Skua
, Stercorarius longicauda, at 310 grams (11 oz), to the Brown Skua
, Stercorarius antarcticus, at 1.63 kg (3.6 lb). On average, a skua is about 56 cm (22 in) long, and 121 cm (48 in) across the wings. They have longish bills with a hooked tip, and webbed feet with sharp claws. They look like large dark gulls, but have a fleshy cere above the upper mandible. The skuas are strong, acrobatic fliers. They are generally aggressive in disposition. Potential predators who go near their nest will be quickly dived at by the parent bird, which usually targets the head of the intruder.
s, wader
s, auk
s, and skimmer
s. In the three smaller species, all nesting exclusively in the Holarctic
, breeding adults have the two central tail feathers obviously elongated, and at least some adults have white on the underparts and pale yellow on the neck. These characteristics are not shared by the larger species, all native to the Southern Hemisphere except for the Great Skua. Therefore the skuas are often split into two genera, with only the smaller species retained in Stercorarius, and the large species placed in Catharacta. However, based on genetics
, behavior, and feather lice
, the overall relationship among the species is best expressed by placing all in a single genus. The Pomarine and Great Skuas' mitochondrial DNA
(inherited from the mother) is in fact more closely related to each other than it is to either Arctic or Long-tailed Skuas, or to the Southern Hemisphere species. Thus, hybridization must have played a considerable role in the evolution of the diversity of Northern Hemisphere skuas.
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...
s with about seven species forming the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Stercorariidae and the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Stercorarius. The three smaller skuas are called jaegers in North America.
The English word "skua" comes from the Faroese
Faroese language
Faroese , is an Insular Nordic language spoken by 48,000 people in the Faroe Islands and about 25,000 Faroese people in Denmark and elsewhere...
name skúgvur ˈskɪkvʊər for the Great Skua
Great Skua
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.-Description:...
, with the island of Skúvoy
Skúvoy
Skúvoy is an island in central Faroe Islands, located to the south of Sandoy. It is named after the large number of skua present on the island . There is only one settlement on the island: Skúvoy on the east coast...
renowned for its colony of that bird. The general Faroese term for skuas is kjógvi ˈtʃɛkvə. The word "jaeger" is derived from the German
German language
German is a West Germanic language, related to and classified alongside English and Dutch. With an estimated 90 – 98 million native speakers, German is one of the world's major languages and is the most widely-spoken first language in the European Union....
word Jäger, meaning "hunter".
Skuas nest on the ground in temperate and Arctic regions, and are long-distance migrants
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...
. They have even been sighted at the South Pole
South Pole
The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is one of the two points where the Earth's axis of rotation intersects its surface. It is the southernmost point on the surface of the Earth and lies on the opposite side of the Earth from the North Pole...
.
Biology and habits
Outside the breeding season, skuas take fish, offalOffal
Offal , also called, especially in the United States, variety meats or organ meats, refers to the internal organs and entrails of a butchered animal. The word does not refer to a particular list of edible organs, which varies by culture and region, but includes most internal organs other than...
, and carrion
Carrion
Carrion refers to the carcass of a dead animal. Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters include vultures, hawks, eagles, hyenas, Virginia Opossum, Tasmanian Devils, coyotes, Komodo dragons, and burying beetles...
. Many are partial kleptoparasites
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...
, comprising up to 95% of the feeding methods of wintering birds, by chasing gulls, terns and other seabirds to steal their catches, regardless of the size of the species attacked (up to 3 times heavier than the attacking skua). The larger species, such as the Great Skua
Great Skua
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.-Description:...
, also regularly kill and eat adult birds, such as puffin
Puffin
Puffins are any of three small species of auk in the bird genus Fratercula with a brightly coloured beak during the breeding season. 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 crevices among...
s and 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, and have been recorded as killing birds as large as a Grey Heron
Grey Heron
The Grey Heron , is a wading bird of the heron family Ardeidae, native throughout temperate Europe and Asia and also parts of Africa. It is resident in the milder south and west, but many birds retreat in winter from the ice in colder regions...
. On the breeding grounds they commonly eat lemming
Lemming
Lemmings are small rodents, usually found in or near the Arctic, in tundra biomes. They are subniveal animals, and together with voles and muskrats, they make up the subfamily Arvicolinae , which forms part of the largest mammal radiation by far, the superfamily Muroidea, which also includes rats,...
s, and the eggs and young of other birds. In the Southern oceans and Antarctica region, some skua species (especially the South Polar Skua
South Polar Skua
The South Polar Skua, Stercorarius maccormicki, is a large seabird in the skua family Stercorariidae. An older name for the bird is MacCormick’s Skua, after explorer and naval surgeon Robert McCormick, who first collected the type specimen...
) will readily scavenge the carcasses at breeding colonies of penguin
Penguin
Penguins are a group of aquatic, flightless birds living almost exclusively in the southern hemisphere, especially in Antarctica. Highly adapted for life in the water, penguins have countershaded dark and white plumage, and their wings have become flippers...
s and pinniped
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...
s, sometimes taking live penguin chicks. In these areas, skuas seem to defer to the considerably larger giant petrel
Giant petrel
Giant petrels is a genus, Macronectes, from the family Procellariidae and consist of two species. They are the largest birds from this family...
s.
Bird
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...
s, typically with grey or brown plumage, often with white markings on the wings. The skuas range in size from the Long-tailed Skua
Long-tailed Skua
The Long-tailed Skua, Stercorarius longicaudus is a seabird in the skua family Stercorariidae....
, Stercorarius longicauda, at 310 grams (11 oz), to the Brown Skua
Brown Skua
The Brown Skua , also known as the Antarctic Skua, Southern Great Skua, Southern Skua, or Hākoakoa , is a large seabird that breeds in the subantarctic and Antarctic zones and moves further north when not breeding...
, Stercorarius antarcticus, at 1.63 kg (3.6 lb). On average, a skua is about 56 cm (22 in) long, and 121 cm (48 in) across the wings. They have longish bills with a hooked tip, and webbed feet with sharp claws. They look like large dark gulls, but have a fleshy cere above the upper mandible. The skuas are strong, acrobatic fliers. They are generally aggressive in disposition. Potential predators who go near their nest will be quickly dived at by the parent bird, which usually targets the head of the intruder.
Taxonomy
Skuas are related to gullGull
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, wader
Wader
Waders, called shorebirds in North America , are members of the order Charadriiformes, excluding the more marine web-footed seabird groups. The latter are the skuas , gulls , terns , skimmers , and auks...
s, auk
Auk
An auk is a bird of the family Alcidae in the order Charadriiformes. Auks are superficially similar to penguins due to their black-and-white colours, their upright posture and some of their habits...
s, and skimmer
Skimmer
The Skimmers, Rynchopidae, are a small family of tern-like birds in the order Charadriiformes, which also includes the waders, gulls and auks. The family comprises three species found in South Asia, Africa, and the Americas....
s. In the three smaller species, all nesting exclusively in the Holarctic
Holarctic
The Holarctic ecozone refers to the habitats found throughout the northern continents of the world as a whole. This region is divided into the Palearctic, consisting of Northern Africa and all of Eurasia, with the exception of Southeast Asia and the Indian subcontinent, and the Nearctic,...
, breeding adults have the two central tail feathers obviously elongated, and at least some adults have white on the underparts and pale yellow on the neck. These characteristics are not shared by the larger species, all native to the Southern Hemisphere except for the Great Skua. Therefore the skuas are often split into two genera, with only the smaller species retained in Stercorarius, and the large species placed in Catharacta. However, based on genetics
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
, behavior, and feather lice
Bird louse
Bird louse refers to any chewing louse of order Phthiraptera which parasitizes warm-blooded animals, especially birds. Bird lice may feed on feathers, skin, or blood. They have no wings, and ther biting mouth parts distinguish them from true lice, which suck blood.Almost all domestic birds are...
, the overall relationship among the species is best expressed by placing all in a single genus. The Pomarine and Great Skuas' mitochondrial DNA
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...
(inherited from the mother) is in fact more closely related to each other than it is to either Arctic or Long-tailed Skuas, or to the Southern Hemisphere species. Thus, hybridization must have played a considerable role in the evolution of the diversity of Northern Hemisphere skuas.
Species
- Long-tailed SkuaLong-tailed SkuaThe Long-tailed Skua, Stercorarius longicaudus is a seabird in the skua family Stercorariidae....
or Long-tailed Jaeger, Stercorarius longicaudus - Parasitic Skua or Arctic Jaeger, Stercorarius parasiticus
- Pomarine SkuaPomarine SkuaThe 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 :...
or Pomarine Jaeger, Stercorarius pomarinus - Chilean SkuaChilean SkuaThe Chilean Skua is a large predatory seabird, which breeds in Argentina and Chile, but ranges as far north as Brazil and Peru when not breeding. A relatively distinctive skua, it has a dark cap that contrasts with its cinnamon throat and lower face...
, Stercorarius chilensis - South Polar SkuaSouth Polar SkuaThe South Polar Skua, Stercorarius maccormicki, is a large seabird in the skua family Stercorariidae. An older name for the bird is MacCormick’s Skua, after explorer and naval surgeon Robert McCormick, who first collected the type specimen...
, Stercorarius maccormicki - Brown SkuaBrown SkuaThe Brown Skua , also known as the Antarctic Skua, Southern Great Skua, Southern Skua, or Hākoakoa , is a large seabird that breeds in the subantarctic and Antarctic zones and moves further north when not breeding...
, Stercorarius antarcticus- Falkland Skua, Stercorarius (antarcticus) antarcticus
- Tristan Skua, Stercorarius (antarcticus) hamiltoni
- Subantarctic Skua, Stercorarius (antarcticus) lonnbergi
- Great SkuaGreat SkuaThe 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.-Description:...
Stercorarius skua
External links
- Skua videos on the Internet Bird Collection