Artic skuas have two main colour morphs; dark and pale, with a number in between that tend towards the dark morph. In all morphs upperparts are dark grey-brown with darker flight feathers. Their wings have a pale crescent-shaped patch. Underwing coverts are dark in all adult arctic skuas.
The dark morph adult Artic skuas have blackish-brown plumage overall with a paler wash on the sides of their neck. The pale morph has a dark head with a yellow wash on the neck. Their underparts are white with a dark breast band.
All Arctic skuas have black bills with a pale upperbase, brown eyes and black legs and webbed feet.
During winter the pale morph has heavily dark-spotted underparts and the breast band is spotted. The dark morph is similar all year round.
Adult male and female Arctic skuas look similar although the female is slightly larger than the male. Juveniles have very varied plumage from pale heads and underparts to uniform dark brown tinged with red.
Arctic skuas build nests on dry tundra, higher fells and islands. It is an unlined scrape usually close to streams or ponds. They may nest near other seabird colonies or scattered apart.
Arctic skuas lay 2 olive-green eggs with dark markings. The eggs are incubated by both adults for 20-27 days. Chicks are precocial when they hatch and are covered in dark brown down. Both parents feed them on regurgitated food. They fledge at 26-30 days.
Artic skuas feed mainly by kleptoparasitism, taking food from other seabirds. They will also hunt for their own, fish, rodents, small birds, mammals and eggs.
Arctic skuas can be found all round the coast of the UK, but mainly in the Shetland and Orkney Islands and the coastal moorlands of north and west Scotland.
The Arctic skua is also knows as the parasitic jaeger. Jaeger is derived from the German word Jäger which means ‘hunter’ and parasitic is due to its feeding habits.