Arctic Skua

Stercorarius parasiticus

41-46cm

Appearance

Both its middle tail feathers and its wings are long and pointed, and the narrow wings have white sections. The sexes resemble each other, however there are two colour morphs. The pale-phase adult is white on the breast, belly and neck, it has a dark cap and may have a greyish brown breast band. Rest of plumage is dark greyish brown, and the cheeks can be subtly tinged with yellow. Dark-phase adults are uniform dark brown. Juveniles are often quite dark and vary in shades of rufous-brown. The bill has a dark tip, upperpart feathers are lined with buff, and the tail is wedge-shaped with small points.

Character

Pursues other seabirds while in flight, pestering them until they relinquish their food. Very territorial when breeding, and can be aggressive towards invaders such as cows and humans. Its wingbeats are deep and powerful and it is an agile flier; breeding occurs in loose colonies and it may migrate alone or in small groups.

Food

Mostly eats fish, particularly sand eels and sprats surrendered by other birds. Scavenges on dead animals including birds, will eat eggs from other birds' nests, and may kill small mammals. Insects and berries may also be eaten.

Breeding

First eggs in Scotland are laid in May. Usually 2 eggs which are incubated for 25-28 days by both sexes; initial egg is incubated immediately so it hatches before the second one. Young can fly at about 25-30 days old and gain independence after 2-5 weeks.

Population

Breeds in Scotland during the summer but is otherwise known as a passage migrant in the region. The migration population around the coasts of the region is highest in September; approximately 2100 pairs breed here each year.

Observation Tips

During breeding season, the coasts of Orkney and Shetland are strongholds, particularly local island reserves. When there are strong onshore winds, birds may be quite numerous further south by the sea.

Voice

Mostly silent, but has a guttural 'ka-aaow' which it may utter near its nest.
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