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Great skua Stercorarius skua

The great skua (Stercorarius skua) is a large seabird in the skua family Stercorariidae. It is roughly the size of a herring gull. It mainly eats fish which is taken from the surface of the sea or from other birds.

Description & appearance

Great skuas measure 50–58 cm (20–23 in) long and have a 125–140 cm (49–55 in) wingspan. One study found that 112 males weighed an average of 1.27 kg (2.8 lb) and that 125 females weighed an average of 1.41 kg (3.1 lb). Adults are a streaked greyish brown, with a black cap, while juveniles are a warmer brown and unstreaked below. They have a short, blunt tail, and a powerful flight. The great 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 (parasitic jaeger, pomarine jaeger and long-tailed jaeger) 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. Identification of this skua is only complicated when it is necessary to distinguish it from the closely related large southern-hemisphere skuas. Despite its name, the great skua is marginally smaller on average than the other 3 large southern-hemisphere skuas, although not by enough to distinguish them by size in the field. 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 taxonomy is not commonly followed.

The great skua is an aggressive pirate of the seas, deliberately harassing birds as large as gannets to steal a free meal. It also readily kills and eats smaller birds such as puffins. Great skuas show little fear of humans - anybody getting close to the nest will be repeatedly dive-bombed by the angry adult. Unusual behaviour by St Kilda's skuas was recorded in 2007 during research into recent falls in the Leach's storm petrel population. Using night vision gear, ecologists observed the skuas preying on the petrels at night, a remarkable strategy for a seabird.

Habitat

The great skua breeds in Iceland, Norway, the Faroe Islands, and on Scottish islands, with some individuals breeding on mainland Scotland and in the northwest of Ireland.

Hunting & food

They eat mainly fish, birds, eggs, carrion, offal, rodents, rabbits, and occasionally berries. They will often obtain fish by robbing gulls, terns and even northern gannets of their catches. They will also directly attack and kill other seabirds, up to the size of Herring Gulls. Like most other skua species, it continues this piratical behaviour throughout the year, showing less agility and more brute force than the smaller skuas when it harasses its victims. A common technique is to fly up to a gannet in mid-air and grab it by the wing, so that it stalls and falls into the sea, where the great skua then physically attacks it until it surrenders its catch. Due to its size, aggressive nature and fierce defence of its nest, the great skua has little to fear from other predators. While fledglings can fall prey to rats, cats or the Arctic fox, healthy adults are threatened only by greater raptors such as the golden eagle, the white-tailed eagle, and more rarely, by the orca.

Breeding, mating & juveniles

They breed on coastal moorland and rocky islands, usually laying two spotted olive-brown eggs in grass-lined nests. Like other skuas, they will fly at the head of a human or other intruder approaching its nest. Although it cannot inflict serious damage, such an experience with a bird of this size is frightening. They are a migrant species, wintering at sea in the Atlantic Ocean and regularly reaching North American waters. Vagrant to Mediterranean countries (e.g. Turkey).

Important Note:

This text is based on the article Great skua from the free encyclopedia Wikipedia and is licensed under the Creative Commons CC-BY-SA 3.0 Unported (short version). A list of the authors is available on Wikipedia.