The skuas are a group of seabirds with about seven species forming the family
Stercorariidae and the genus Stercorarius. The three smaller skuas
are called jaegers in the Americas. The English word "skua" comes from the
Faroese name skúgvur [ˈskɪkvʊər] for the great skua, with the island of Skúvoy
renowned for its colony of that bird. The general Faroese term for skuas is
kjógvi [ˈtʃɛkvə]. The word "jaeger" is derived from the German word Jäger,
meaning "hunter". Skuas nest on the ground in temperate
and Arctic regions, and are long-distance migrants. They have even
been sighted at the South Pole. Biology and habits
Outside the breeding season, skuas take fish, offal, and carrion. Many are
partial kleptoparasites, comprising up to 95% of the feeding methods of
wintering birds, by chasing gulls, terns and other seabirds to steal their
catches, regardless of the size of the species attacked. The larger species,
such as the great skua, also regularly kill and eat adult birds, such as
puffins and gulls, and have been recorded as killing birds as large as a
grey heron. 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
young of other birds are an important food source for most skua species during
the nesting season. In the southern oceans and Antarctica region, some skua
species will readily scavenge the carcasses at breeding colonies of
penguins and pinnipeds, sometimes taking live penguin chicks. In these areas,
skuas seem to defer to the considerably larger giant petrels.
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 310 grams, to the brown
skua, Stercorarius antarcticus, at 1.63 kg. On average, a skua is about 56 cm
long, and 121 cm 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 who go
near their nest will be quickly dived at by the parent bird, which usually
targets the head of the intruder - a practice known as 'dive bombing'.
Taxonomy Skuas are related to gulls, waders,
auks, and skimmers. In the three smaller species, all nesting exclusively in the
Holarctic, 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, 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 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. Thus, hybridization must have played a considerable role in
the evolution of the diversity of Northern Hemisphere skuas.
Species References
Harrison, Peter Seabirds: An Identification Guide ISBN 0-7470-1410-8
External links Skua videos on the Internet Bird
Collection