The great skua (Stercorarius skua), sometimes known by the name bonxie in Britain, is a large seabird in the skua family Stercorariidae. It is roughly the size of a herring gull. It mainly eats fish caught at the sea surface or taken from other birds.

Taxonomy

The great skua was described from the Faroe Islands and Iceland by the Danish zoologist Morten Thrane Brünnich in 1764 under the binomial name Catharacta skua. It is now placed in the genus Stercorarius that was introduced by the French zoologist Mathurin Jacques Brisson in 1760. The English name and species name "skua" is believed to originate from the Faroese or and is the only known bird name to originate from the Faroes that has come into regular use elsewhere. In Britain, it is sometimes known by the name bonxie, a Shetland name of Norse origin. The species is monotypic: no subspecies are recognised.

right|thumb|Great skua robbing a [[northern gannet near Stac an Armin (St Kilda, Scotland)]]

It will often obtain fish by robbing gulls, terns and even northern gannets of their catches. It 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, at sea by the orca.

Predation account

An aerial apex predator, the great skua is also an aggressive kleptoparasite, 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 to no fear of humans – anybody getting close to the nest will be repeatedly dive-bombed by the territorial adults.

<!--Read more at https://www.rspb.org.uk/birds-and-wildlife/wildlife-guides/bird-a-z/great-skua#6JHZvij5hIe43rqm.99-->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.

Further reading

  • at the Handa Island Skua Project