The skuas are a group of predatory
seabirds with seven species forming the
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
''Stercorarius'', the only genus in the
family Stercorariidae. The three smaller skuas, the
long-tailed skua, the
Arctic skua, and the
pomarine skua are called jaegers in
North American English
North American English (NAmE, NAE) is the most generalized variety of the English language as spoken in the United States and Canada. Because of their related histories and cultures, plus the similarities between the pronunciations (accents), ...
.
The English word "skua" comes from the
Faroese name for the
great skua, , with the island of
Skúvoy renowned for its colony of that bird. The general Faroese term for skuas is . The word "jaeger" is derived from the
German
German(s) may refer to:
* Germany (of or related to)
**Germania (historical use)
* Germans, citizens of Germany, people of German ancestry, or native speakers of the German language
** For citizens of Germany, see also German nationality law
**Ge ...
word , meaning "hunter".
The genus name ''Stercorarius'' is
Latin
Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
and means "of dung"; because the food disgorged by other birds when pursued by skuas was once thought to be excrement.
Skuas nest on the ground in
temperate and
Arctic regions, and are long-distance
migrants. They have even been sighted at the
South Pole
The South Pole, also known as the Geographic South Pole, Terrestrial South Pole or 90th Parallel South, is one of the two points where Earth's axis of rotation intersects its surface. It is the southernmost point on Earth and lies antipod ...
.
Biology and habits
Outside the breeding season, skuas take fish,
offal, and
carrion. Many practice
kleptoparasitism, which comprises up to 95% of the feeding methods of wintering skuas, by chasing gulls, terns and other seabirds to steal their catches, regardless of the size of the species attacked (up to three times heavier than the attacking skua). The larger species, such as the
great skua, also regularly kill and eat adult birds, such as
puffins and
gulls, and have been seen killing birds as large as a
grey heron
The grey heron (''Ardea cinerea'') is a long-legged wading bird of the heron family, Ardeidae, native throughout temperate Europe and Asia and also parts of Africa. It is resident in much of its range, but some populations from the more north ...
. On the breeding grounds, the three, more slender northern breeding species commonly eat
lemmings. Those species that breed in the southern oceans largely feed on fish that can be caught near their colonies. The eggs and chicks of other seabirds, primarily
penguins, are an important food source for most skua species during the nesting season.
In the southern oceans and
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...
region, some skua species (especially the
south polar skua) will readily scavenge carcasses at breeding colonies of both
penguins and
pinniped
Pinnipeds (pronounced ), commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant families Odobenidae (whose only living member is the ...
s. Skuas will also kill live penguin chicks. In these areas, the skuas will often forfeit their catches to the considerably larger and very aggressive
giant petrels. Skuas have also been observed to directly pilfer
milk
Milk is a white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals (including breastfed human infants) before they are able to digest solid food. Immune factors and immune-modulat ...
from the
elephant seal's teat.
They are medium to large
birds, typically with grey or brown plumage, often with white markings on the wings.
[ The skuas range in size from the long-tailed skua, ''Stercorarius longicauda'', at , to the brown skua, ''Stercorarius antarcticus'', at . On average, a skua is about long, and across the wings. They have longish bills with a hooked tip, and webbed feet with sharp claws. They look like large dark gulls, but have a fleshy cere above the upper mandible.
The skuas are strong, acrobatic fliers. They are generally aggressive in disposition. Potential predators approaching their nests will be quickly attacked by the parent birds, which usually target the heads of intruders – a practice known as ' divebombing'.
]
Taxonomy
The genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
''Stercorarius'' was introduced by the French zoologist Mathurin Jacques Brisson
Mathurin Jacques Brisson (; 30 April 1723 – 23 June 1806) was a French zoologist and natural philosopher.
Brisson was born at Fontenay-le-Comte. The earlier part of his life was spent in the pursuit of natural history; his published wo ...
in 1760 with the parasitic jaeger (''Stercorarius parasiticus'') as the type species
In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specim ...
.
Skuas are related to gulls, waders, auk
An auk or alcid is a bird of the family Alcidae in the order Charadriiformes. The alcid family includes the murres, guillemots, auklets, puffins, and murrelets. The word "auk" is derived from Icelandic ''álka'', from Old Norse ''alka'' (a ...
s, and skimmer
Skimmer may refer to: Animals
*Skimmer (bird), a common name for birds in the genus ''Rynchops''
*Skimmer (dragonfly), a common name for dragonflies in the family Libellulidae
*Water strider or skimmer, a common name for insects in the family Ge ...
s. In the three smaller species, all nesting exclusively in the Holarctic
The Holarctic realm is a biogeographic realm that comprises the majority of habitats found throughout the continents in the Northern Hemisphere. It corresponds to the floristic Boreal Kingdom. It includes both the Nearctic zoogeographical reg ...
, breeding adults have the two central tail feathers obviously elongated, and at least some adults have white on the underparts and pale yellow on the neck. These characteristics are not shared by the larger species, all native to the Southern Hemisphere except for the great skua. Therefore, the skuas are often split into two genera, with only the smaller species retained in ''Stercorarius'', and the large species placed in ''Catharacta''. However, based on genetics
Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar work ...
, behavior, and feather lice, the overall relationship among the species is best expressed by placing all in a single genus. The pomarine and great skuas' mitochondrial DNA (inherited from the mother) is in fact more closely related to each other than it is to either Arctic or long-tailed skuas, or to the Southern Hemisphere species.[Cohen, Baker, Belchschmidt, Dittmann, Furness, Gerwin, Helbig, de Korte, Marshall, Palma, Peter, Ramli, Siebold, Willcox, Wilson and Zink (1997)]
Enigmatic phylogeny of skuas.
''Proc. Biol. Sci.'' 264(1379):181–190. Thus, hybridization
Hybridization (or hybridisation) may refer to:
*Hybridization (biology), the process of combining different varieties of organisms to create a hybrid
*Orbital hybridization, in chemistry, the mixing of atomic orbitals into new hybrid orbitals
*Nu ...
must have played a considerable role in the evolution of the diversity of Northern Hemisphere skuas.
Species
The genus contains seven species:
References
External links
*
Skua videos
on the Internet Bird Collection
{{Authority control
Seabirds
Taxa named by Mathurin Jacques Brisson