Appearance
Identification is complicated by similarities to long-tailed jaeger and pomarine skua, and the existence of three colour morphs. Small for a skua, the parasitic jaeger measures 41–48 cm in length, 107–125 cm in wingspan and weighs 300–650 g. The tail streamer of the breeding adult accounts for about 7 cm of their length.Light-morph 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-morph adults are dark brown, and intermediate-phase birds are dark with somewhat paler underparts, head and neck. All morphs have the white wing flash.
Identification of juveniles is even more problematic, and it is difficult to separate parasitic jaegers from long-tailed jaegers. Parasitic jaegers are bulkier, shorter-winged, and less tern-like than long-tailed jaegers. They are usually warmer toned, with browner shades, rather than grey. However, they show the same wide range of plumage variation. The flight is more falcon-like.
Naming
The word "jaeger" is derived from the German word ''Jäger'', meaning "hunter". The English "skua" comes from the Faroese name ''skúgvur'' [ˈskɪkvʊər] for the great skua, with the island of Skúvoy known for its colony of that bird. The general Faroese term for skuas is ''kjógvi'' [ˈtʃɛkvə]. The genus name ''Stercorarius'' is Latin and means "of dung"; the food disgorged by other birds when pursued by skuas was once thought to be excrement. The specific ''parasiticus'' is from Latin and means "parasitic".
Reproduction
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 mewing 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.
Food
This bird will feed on rodents, small birds and insects. It also robs gulls and terns of their catches.References:
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