Great skua

The great skua (Stercorarius skua) has been described as the “pirate of the seas” for its habit of stealing food from other birds. It is not alone among the skua species for doing this, but it is particularly aggressive in its behaviour and shows no fear of any other creature, including man.

Appearance

The great skua is around 58 centimetres (23 inches) long, stocky in build, and with a shorter wingspan than other skuas, the wings also being shorter, broader and less pointed. All skua species have protruding central tail feathers, but in the great skua these are relatively short. The plumage is dark brown above, and greyish or reddish brown below. The wings are particularly elegant, with the feathers of each layer having a different shade of brown or dark grey, set off by a prominent white flash. This makes the great skua very recognisable in flight. Males and females have similar plumage.

Behaviour

When not being piratical, the great skua might seem to be heavy and laboured as it flies, but when the chase is on it’s a different story! The target might be a tern, gull or gannet which has dived to gather a fish but then finds itself under attack from a great skua. The latter will twist in any direction to harass the “victim”, and even grab hold of a wing or tail until the food is dropped or regurgitated. The great skua will then drop down to grab the food before it hits the water.

Smaller birds, such as puffins, are themselves taken as food by great skuas, as are the eggs of other birds. The great skua will feed on whatever it can find, including insects, carrion, and small mammals. It does not always steal fish, as it is happy to dive for its own, spending more time settled on the surface than other skuas.

Great skuas spend most of their lives at sea, coming ashore only to breed. In the Northern Hemisphere their breeding grounds include the northern and western isles of Scotland, while southern hemisphere skuas are found on the coasts of Antarctica and Tierra del Fuego.

Breeding

Nesting is often in diffuse colonies, or a pair may nest remotely from other birds. Nests are made on moors or marshy ground not far from the coast. The clutch of two eggs is laid in May or June, and both birds incubate them for up to 30 days. A lost clutch will be replaced, but only one brood is raised each season. While at the nest, the adult birds are very defensive, not allowing any potential threat to get close. A great skua might dive-bomb an unwise walker who has strayed into their territory, or fly in low then rise up at the last second to attack with the feet.

However, when not in attack mode the great skua appears ungainly, waddling around the nest site, bathing in any nearby pool, or standing guard on a mound or tussock.

The young are fed at the nest for six or seven weeks, after which all the birds fly off to sea, where they may range as far south as Spain. The best time to see great skuas, if you do not wish to risk their anger by trying to view them onshore, is when they are migrating in late summer or early autumn along the Atlantic and North Sea coasts of the UK.

The photo was taken by me on Loch Gairloch in northwest Scotland.

© John Welford