Stercorarius parasiticus

Cladus: Eukaryota
Supergroup: Opisthokonta
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Superclassis: Tetrapoda
Classis: Aves
Subclassis: Carinatae
Infraclassis: Neornithes
Parvclassis: Neognathae
Ordo: Charadriiformes
Subordo: Lari
Familia: Stercorariidae
Genus: Stercorarius
Species: Stercorarius parasiticus

Name

Stercorarius parasiticus (Linnaeus, 1758)

Vernacular names
Internationalization
Български: Среден морелетник
Česky: Chaluha příživná
Cymraeg: Sgiwen y Gogledd
Deutsch: Schmarotzerraubmöwe
Ελληνικά: Γερακοληστόγλαρος
English: Arctic Skua
Esperanto: Parazita rabmevo
Español: Escúa ártica
Italiano: Labbo
日本語: クロトウゾクカモメ
한국어: 북극도둑갈매기
Lietuvių: Smailiauodegis plėšikas
Nederlands: Kleine jager
Polski: Wydrzyk ostrosterny
Suomi: Merikihu
Svenska: Kustlabb

------

The Parasitic Jaeger, also known as the Arctic Skua or Parasitic Skua, (Stercorarius parasiticus) is a seabird in the skua family Stercorariidae.

This species breeds in the north of Eurasia and North America, with significant populations as far south as northern Scotland. It nests on dry tundra, higher fells and islands, laying up to four olive-brown eggs. It is usually silent except for newing and wailing notes while on the breeding grounds. Like other skuas, it will fly at the head of a human or fox approaching its nest. Although it cannot inflict serious damage, it is a frightening and painful experience. It is a migrant, wintering at sea in the tropics and southern oceans.

In the British Isles, they breed in Shetland and Orkney, the Outer Hebrides, Sutherland, Caithness, and some islands in Argyll.

This bird will feed on rodents, small birds and insects but also robs gulls and terns of their catches. Like the larger skua species, it continues this piratical behaviour throughout the year, showing great agility as it harasses its victims.
Identification of this skua is complicated by its similarities to Long-tailed Skua and Pomarine Skua, and the existence of three colour phases. This is one of the smaller skuas at about 41 cm length, excluding the pointed central tail feathers of the summer adult, which can add another 7 cm or so. Light phase adults 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 and there is a pointed central tail projection. Dark phase adults are dark brown, and intermediate phase birds are dark with somewhat paler underparts, head and neck. All phases have the white wing flash.

Juveniles are even more problematic, and are difficult to separate from Long-tailed Skua over the sea. They are bulkier, shorter-winged and less tern-like than that species, but show the same wide range of plumage variation. The flight is more falcon-like. However, they are usually warmer toned than Long-tailed, with browner shades, rather than grey.
References

* BirdLife International (2004). Stercorarius parasiticus. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 12 May 2006. Database entry includes justification for why this species is of least concern
* Harrison, Peter (1996). Seabirds of the World. Princeton: Princeton University Press. ISBN 0-691-01551-1.
* Bull, John; Farrand, Jr., John (April 1984). The Audubon Society Field Guide to North American Birds, Eastern Region. New York: Alfred A. Knopf. ISBN 0-394-41405-5.