This is a large skua at about 45cm length, excluding the central tail feathers of the summer adult, which can add another 10cm or so.
This species breeds in the far north of Eurasia and North America. It nests on arctic tundra and islands, laying 2-3 eggs. Like other skuas, it will fly at the head of a human or other intruder 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 tropical oceans.
This bird will feed on lemmings and other rodents on the breeding grounds, but also robs gulls, terns and even Gannets of their catches. Like most other 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 Arctic Skua and the existence of three colour phases. Pomarine Skuas are larger than Common Gulls. They are much bulkier, longer-winged and less falcon-like than Arctic Skua, but show the same wide range of plumage variation. The flight is more measured than the smaller species.
Light phase adult Pomarine Skuas 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 long spoon-shaped 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, which appears as a diagnostic double flash on the underwing.
Juveniles are even more problematic to identify, and are difficult to separate from Arctic Skua over the sea on plumage alone.