Great skua

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Great skua

Least Concern (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Charadriiformes
Family: Stercorariidae
Genus: Stercorarius
Species:
S. skua
Binomial name
Stercorarius skua
(Brünnich, 1764)
Synonyms

Catharacta skua

The great skua (Stercorarius skua), sometimes known by the name bonxie in Britain, is a large

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

monotypic: no subspecies are recognised.[5]

Description

Displaying white wing flashes

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 lb 13 oz) and that 125 females weighed an average of 1.41 kg (3 lb 2 oz).[11] 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.[11] 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.

Great skua, as another pair flew too close to their nest site (Shetland)

Origins

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,[12] 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 jaeger for details).

Breeding

Egg, Collection Museum Wiesbaden

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. 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 their 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. They are vagrant to Mediterranean countries (e.g. Turkey).

Diet

They eat mainly fish, birds,

eggs, carrion, offal, rodents, rabbits, and occasionally berries. They have been known to prey on lambs, and even pony foals. Probably their most prolific food source is by-catch abandoned by fishing vessels.[13]

Great skua robbing a northern gannet near Stac an Armin (St Kilda, Scotland)

They will often obtain fish by robbing

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 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 to no fear of humans – anybody getting close to the nest will be repeatedly dive-bombed by the angry adults. 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.[14]

Gallery

  • Great skua in water
    Great skua in water
  • At the Norwegian bird island Runde
    At the Norwegian bird island Runde
  • At Runde
    At Runde
  • In flight.
    In flight.
  • Great skua at North Sea island Hallig Hooge / Germany
    Great skua at North Sea island Hallig Hooge / Germany
  • At Handa Island / Scotland
    At Handa Island / Scotland
  • Museum specimen
    Museum specimen

References

  1. ^ BirdLife International (2012). "Catharacta skua". IUCN Red List of Threatened Species. 2012. Retrieved 24 April 2016.
  2. ^ Brünnich, Morten Thrane (1764). M. Th. Brünnichii Ornithologia borealis, sistens collectionem avium : ex omnibus, Imperio danico subjectis, provinciis insulisqve borealibus Hafniæ factam, cum descriptionibus novarum, nominibus incolarum, locis natalium et icone (in Latin). Hafniae [Copenhagen]: Typis Andreæ Hartvigii Godiche. pp. 33–36.
  3. ^ Peters, James Lee, ed. (1934). Check-List of Birds of the World. Vol. 2. Cambridge, Massachusetts: Harvard University Press. pp. 309–310.
  4. ^ Brisson, Mathurin Jacques (1760). Ornithologie, ou, Méthode Contenant la Division des Oiseaux en Ordres, Sections, Genres, Especes & leurs Variétés (in French and Latin). Paris: Jean-Baptiste Bauche. Vol. 1, p. 56, Vol. 6, p. 149.
  5. ^
    Rasmussen, Pamela, eds. (2020). "Noddies, gulls, terns, auks"
    . IOC World Bird List Version 10.1. International Ornithologists' Union. Retrieved 4 June 2020.
  6. ^ Salomonsen, F. (1935). "Den færøiske ornithologis historie indtil aar 1800 supplement". Dansk Ornithologisk Forenings Tidsskrift (in Danish): 67–100.
  7. ^ "Skua". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  8. ^ English Review Magazine, vol. 2–3, Eyre and Spottiswoode limited., 1949, p. 369
  9. ^ "Dictionary of the Scots Language".
  10. .
  11. ^ .
  12. .
  13. ^ "Foula: Britain's most remote inhabited island".
  14. ^ McKenzie, Steven (5 November 2007). "Bird night attacks may be unique". BBC News. Retrieved 6 November 2007.

External links