UKBirds

Great Skua

Stercorarius skua

The Great Skua, Stercorarius skua, is a large seabird in the skua family Stercorariidae. In Britain, it is sometimes known by the name Bonxie, a Shetland name of unknown origin.

This is a large skua, measuring 50-58 cm (20-23 in) in length with a 125-140 cm (49-55 in) wingspan. The adult is streaked greyish brown, with a black cap, while the juvenile is a warmer brown and unstreaked below. Its tail is short and blunt. The flight is direct and powerful. The Brown Skua's call is a harsh hah-hah-hah-hah; quacking and croaking noises have also been heard. Distinguishing this skua from the other North Atlantic skuas (Arctic Skua, Pomarine Skua and Long-tailed Skua) is relatively straightforward. The Herring Gull size, massive barrel chest and white wing flashes of this bird are distinctive even at a distance. It is sometimes said to give the impression of a Common Buzzard (which in America would be called a hawk). Identification of this skua is only complicated when it is necessary to distinguish it from the closely related large southern-hemisphere skuas. Some authorities still regard the Great Skua as conspecific with some of these southern skuas, and as a group they have sometimes been separated in the genus Catharacta, although currently this is not commonly followed.

Genetic studies have found surprising similarities between the Great Skua and the Pomarine Skua, despite their dissimilar appearance. Many ornithologists now believe either that the Great Skua originated as a hybrid between the Pomarine Skua and one of the southern-hemisphere species [Furness and Hamer, 2003], presumably as a result of vagrancy or migration across the equator by the southern species, or that the Pomarine Skua evolved from hybridization of the Great Skua and one of the small Arctic species (see Pomarine Skua for details).