Scientific name: Stercorarius pomarinus (Temminck, 1815)
Bird group: Skuas
Field characters. 50 cm. A heavy, robust gull-like bird with elongated, twisted rectrices. Two morphs: a light one (common, about 90%) and a dark one (rare). Light morph with black face and "cap"; sides of nape yellowish, rest of upperparts ranging from sooty to brown-grey; cheeks, throat and underparts white, frequently with band of dusky flecks on chest and dusky barring on flanks, lower belly and vent. Dark morph completely brown at all times of year. In flight, both morphs have brownish- black wings with whitish bases of primaries; rounded and twisted rectrices give tail peculiar heavy look. Base of wings clearly broader than in Arctic Skua. In winter, upperbody of light morph becomes paler due to buffish or off-white feather-margins; white of neck and face with dark spots; chest with dark band; flank and tail-coverts with black and white bars. Juveniles are difficult to separate from Arctic Skua, but breast heavier; central tail feathers squarish and hardly extending (short and pointed in Arctic Skua); usually darker coloured than Arctic and Long-tailed Skua; double pale patch on underwing (only one in Arctic); rump and undertail-coverts are regularly barred (Arctic's bars more irregular and blurred). Often migrates in small parties.
Voice. Most often heard is a sharp "which-yew"; utters also sounds reminiscent of a madman's laughter.
Distribution. Breeding populations fluctuate strongly; they are present in great numbers one year and totally absent the next. Vagrant to inland Europe and Mediterranean, regular on western coasts.
Habitat. Breeds on coastal tundra. On passage mainly oceanic, but regularly seen at coasts.
Food. During breeding season mainly small mammals and eggs and chicks of birds. Outside breeding season a predator and scavenger which feeds on fish and carrion, and occasionally on other birds. Pursues gulls and forces them to disgorge food.