Skua
| Skuas | |
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| Pomarine Skua | |
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| Family: | Stercorariidae Gray, 1871
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| Genus: | Stercorarius Brisson, 1760
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| Species | |
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See Text | |
A skua (Template:Pron-en) is a seabird of the family Stercorariidae. The three smaller skuas are called jaegers in North America.
The name skua comes from Faroese skúgvur [ˈskɪkvʊər], but this word only applies to the species Stercorarius skua, and the island of Skúvoy is renowned for its colony of that bird. The generic Faroese term for a skua is kjógvi ['tʃɛkvə]. 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.[1]
Biology and habits
Outside the breeding season, skuas take fish, offal and carrion. Many are partial kleptoparasites (comprising up to 95% of the feeding methods of wintering birds), 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 Great Skua also regularly kill and eat adult birds, such as puffins and gulls, and have been recorded as killing birds of the size of a Grey Heron.[2] On the breeding grounds they commonly eat lemmings, and the eggs and young of other birds[3].
They are in general medium to large birds, typically with grey or brown plumage, often with white markings on the wings[3]. 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) and 121 (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 a parent skuas, which usually target the head of the intruder.
Taxonomy
Skuas are related to gulls, waders, auks and skimmers. In the three smaller species (all 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, characteristics that the larger species (all native to the Southern Hemisphere except for the Great Skua) do not share. 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, there is no genetic basis for this separation[citation needed]. The Pomarine and Great Skuas' mitochondrial DNA (which is inherited from the mother only) 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[citation needed]. Thus, hybridization must have played a considerable role in the evolution of the diversity of Northern Hemisphere skuas.
Species
- Long-tailed Skua or Long-tailed Jaeger, Stercorarius longicaudus
- Parasitic Skua or Arctic Jaeger, Stercorarius parasiticus
- Pomarine Skua or Pomarine Jaeger, Stercorarius pomarinus
- Chilean Skua, Stercorarius chilensis
- South Polar Skua, Stercorarius maccormicki
- Brown Skua, Stercorarius antarctica
- Falkland Skua, Stercorarius (antarctica) antarctica
- Tristan Skua, Stercorarius (antarctica) hamiltoni
- Subantarctic Skua, Stercorarius (antarctica) lonnbergi
- Great Skua Stercorarius skua
References
- ^ Mark Sabbatini, "Non-human life form seen at Pole", The Antarctic Sun, 5 January 2003.
- ^ Scottish Ornithologists' Club
- ^ a b Harrison, Colin J.O. (1991). Forshaw, Joseph (ed.). Encyclopaedia of Animals: Birds. London: Merehurst Press. p. 109. ISBN 1-85391-186-0.
- Harrison, Peter Seabirds: An Identification Guide ISBN 0-7470-1410-8
External links
select an article title from: Wikisource:1911 Encyclopædia Britannica
- Skua videos on the Internet Bird Collection