The pomarine jaeger (''Stercorarius pomarinus''), pomarine skua, or pomatorhine skua, is a

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 The skuas are a group of predatory seabirds with seven species forming the genus ''Stercorarius'', the only genus in the family Stercorariidae. The three smaller skuas, the long-tailed skua, the Arctic skua, and the pomarine skua are called ...

family Stercorariidae. It is a migrant, wintering at sea in the tropical oceans.

Taxonomy

Its relationships are not fully resolved; its mitochondrial DNA is most similar to the great skua, but from morphology and behavior, it is closer to the lesser skuas (such as the parasitic jaeger). The most likely explanation is extensive hybridization between the great and one species of lesser skuas, which resulted in a hybrid population that eventually evolved into a distinct species, the pomarine jaeger; or alternatively between the pomarine and a species of Southern Hemisphere skua, with the great skua being the hybrid offspring, perhaps appearing as recently as the 15th century. Judging from characteristics of the skeleton and behavior, the former seems more likely, as the pomarine jaeger shares several similarities with the "Catharacta" skuas, while the great skua does not seem much different from its Southern Hemisphere relatives. The mtDNA difference between the pomarine jaeger and the great skua is one of the smallest between any two vertebrate species yet analyzed, being less than the variation found between different individuals of widespread species. The apparent capability for hybridization has led to the abolition of the separate genus ''Catharacta'' for the Southern Hemisphere and great skuas.

Etymology

The word "jaeger" is derived from the

German German(s) may refer to: * Germany (of or related to) ** Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ge ...

word ''Jäger'', meaning "hunter". 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 specific ''Pomatorhinus'' is from

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...

''poma, pomatos'', "lid" and ''rhis, rhinos'', "nostrils". This refers to the

cere The beak, bill, or rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for eating, preening, manipulating objects, killing prey, fighting, probing for food ...

, which the pomarine jaeger shares with the other skuas. Although it is sometimes erroneously referred to as the Pomeranian skua, the name of this species is unrelated to the

Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden and the North and Central European Plain. The sea stretches from 53°N to 66°N latitude and ...

region of

Pomerania Pomerania ( pl, Pomorze; german: Pommern; Kashubian: ''Pòmòrskô''; sv, Pommern) is a historical region on the southern shore of the Baltic Sea in Central Europe, split between Poland and Germany. The western part of Pomerania belongs to ...

Description

This species ranges from in length, in wingspan and in weight. The upper limit of the length includes the elongated tail streamer of breeding adults, which is about in length. Identification of this jaeger is complicated by its similarities to parasitic jaeger and the existence of three morphs. Pomarine jaegers are larger than

common gull The common gull or sea mew (''Larus canus'') is a medium-sized gull that breeds in the Palearctic, northern Europe. The closely related short-billed gull is sometimes included in this species, which may be known collectively as "mew gull". Man ...

s. They are much bulkier, broader-winged and less

falcon Falcons () are birds of prey in the genus ''Falco'', which includes about 40 species. Falcons are widely distributed on all continents of the world except Antarctica, though closely related raptors did occur there in the Eocene. Adult falcons ...

-like than the parasitic jaeger, but show the same wide range of plumage variation. The flight is more measured than that of the smaller species. It has many harsh chattering calls and others which sounds like ''which-yew''. Light-morph adult pomarine jaegers have a brown back, mainly white underparts and dark primary wing feathers with a white "flash". The head and neck are yellowish-white with a black cap. Dark morph adults are dark brown, and intermediate morph birds are dark with somewhat paler underparts, head and neck. All morphs have the white wing flash, which appears as a diagnostic double flash on the underwing. In breeding adults of all morphs, the two central tail feathers are much longer than the others, spoon-shaped, and twisted from the horizontal. Juveniles are even more problematic to identify, and are difficult to separate from parasitic jaegers at a distance on plumage alone.

Behaviour

Breeding

This species breeds in the far north of

Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago ...

and North America. It nests on Arctic

tundra In physical geography, tundra () is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. The term ''tundra'' comes through Russian (') from the Kildin Sámi word (') meaning "uplands", "treeless mou ...

and islands, laying 2–3 olive-brown eggs in grass lined depressions. Like other skuas, it will fly at the head of a human or other intruder approaching its nest. Although it cannot inflict serious damage, the experience is frightening and painful.

Feeding

This

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

feeds on

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...

, carrion, scraps, smaller

s up to the size of

and

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, especially

lemming A lemming is a small rodent, usually found in or near the Arctic in tundra biomes. Lemmings form the subfamily Arvicolinae (also known as Microtinae) together with voles and muskrats, which form part of the superfamily Muroidea, which also includ ...

s. It robs

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 ...

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

gannets Gannets are seabirds comprising the genus ''Morus'' in the family Sulidae, closely related to boobies. Gannets are large white birds with yellowish heads; black-tipped wings; and long bills. Northern gannets are the largest seabirds in the N ...

of their catches. 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 great agility as it harasses its victims. Only the Great Black Backed Gull, White-Tailed Eagle and Golden Eagle are known to take adult, healthy pomarine skuas.

References

External links

Pomarine skua species text in The Atlas of Southern African Birds
* * * * * * * {{Taxonbar, from=Q212767

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 ...

jaeger, pomarine

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