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Stercorariidae - Skuas or Jaegers

Skua
Brown Skua Stercorarius antarcticus ©James Lowen Website

The Stercorariidae known as skuas or jaegers are a group of seabirds in onee genus, Stercorarius.

They nest on the ground in temperate and Arctic regions, and are long-distance migrants. They have even been sighted at the South Pole.

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 (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 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.

n the southern oceans and Antarctica region, some skua species (especially the South Polar Skua) 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 1.63kg. On average, a skua is about 56cm long, and 121cm wingspan. 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'

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, behaviour, and feather lice, the overall relationship among the species is best expressed by placing all in a single genus. The Pomarine Skua's and Great Skuas' mitochondrial DNA (inherited from the mother) is in fact more closely related to each other than it is to either Arctic Skua or Long-tailed Skua, or to the Southern Hemisphere species. Thus, hybridization must have played a considerable role in the evolution of the diversity of Northern Hemisphere skuas.

There are generally accepted to be just 7 species of Jaegers or Skuas, which are:

Chilean Skua Stercorarius chilensis
South Polar Skua Stercorarius maccormicki
Brown Skua Stercorarius antarcticus
Great Skua Stercorarius skua
Pomarine Skua (Jaeger) Stercorarius pomarinus
Arctic (Parasitic) Skua (Jaeger) Stercorarius parasiticus
Long-tailed Skua (Jaeger) Stercorarius longicaudus

Family Links

Skuas Stercorariidae

Family Account

The skuas /ˈskjuːə/ 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.

Skuas Stercorariidae

RSPB Family Account

Skuas Stercorariidae

Family Account

There are three types of jaegers found in North America.

Species Links

South-polar Skua Stercorarius maccormicki

Species Account

Skuas are similar to jaegers but are bulkier, thicker-necked, and with more prominent wing patches. South Polar Skua is similar to Great Skua but lacks heavy streaking on the body and wing coverts and lacks reddish-brown tones to plumage instead being dark brown to grayish…

South-polar Skua Stercorarius maccormicki

BirdLife Species Account

South-polar Skua Stercorarius maccormicki

IUCN Species Status

South-polar Skua Stercorarius maccormicki

Species Account

Sound archive and distribution map.

South-polar Skua Stercorarius maccormicki

Cornell Species Account

Familiar to North American birders as a pirating brute of the pelagic zone, the South Polar Skua is one of the smaller members of the Stercorarius skuas that breed along the margins of the Southern Ocean.

South-polar Skua Stercorarius maccormicki

HBW Species Account

Taxonomy: Stercorarius maccormicki H. Saunders, 1893, Victoria Land, Antarctica. In past, sometimes considered conspecific with all three congeners. Occasional hybridization with C. antarctica lonnbergi reported. Monotypic.

Brown Skua Stercorarius antarcticus

Species Account

The brown skua (Stercorarius antarcticus), also known as the Antarctic skua, subantarctic skua, southern great skua, southern skua, or hākoakoa (Māori), is a large seabird that breeds in the subantarctic and Antarctic zones and moves further north when not breeding.

Brown Skua Stercorarius antarcticus

BirdLife Species Account

Brown Skua Stercorarius antarcticus

Cornell Species Account

Brown Skua comprises several taxa along the coasts of the Southern Ocean that have been reorganized several times.

Brown Skua Stercorarius antarcticus

Species Account

Sound archive and distribution map.

Brown Skua Stercorarius antarcticus

HBW Species Account

Taxonomy: Lestris antarcticus Lesson, 1831, Falkland Islands. In past, sometimes considered conspecific with all three congeners. Often treated as conspecific with C. skua, but mitochondrial DNA, plumage and biometrics all indicate specific status for both forms; moreover, differs more from C. skua than from other two congeners. Occasional hybridization with C. maccormicki and with C. chilensis reported, but hybrids very rare. Race hamiltoni differs only slightly from nominate. Race lonnbergi has been considered a separate species (name sometimes spelt erroneously as loennbergi, but removal of Scandinavian diacritical mark does not justify addition of “e”). Proposed races clarkei (South Orkneys) and intercedens (Kerguelen I) both considered synonyms of lonnbergi. Three subspecies recognized.

Chilean Skua Stercorarius chilensis

Species Account

The Chilean skua, also called the cinnamon skua (Stercorarius chilensis), is a large predatory seabird, which breeds in Argentina and Chile, but ranges as far north as Brazil and Peru when not breeding.

Chilean Skua Stercorarius chilensis

Cornell Species Account

The large skuas, formerly Catharacta, are a taxonomic problem of great proportions, and also an identification nightmare.

Chilean Skua Stercorarius chilensis

IUCN Species Status

Chilean Skua Stercorarius chilensis

Species Account

Sound archive and distribution map.

Chilean Skua Stercorarius chilensis

BirdLife Species Account

Great Skua Stercorarius skua

Species Account

The great skua (Stercorarius skua) is a large seabird in the skua family Stercorariidae.

Great Skua Stercorarius skua

BirdLife Species Account

Great Skua Stercorarius skua

Species Account

Sound archive and distribution map.

Pomarine Skua (Jaeger) Stercorarius pomarinus

Species Account

The pomarine skua (Stercorarius pomarinus) or pomatorhine skua, known as pomarine jaeger in the Americas, is a seabird in the skua family Stercorariidae. It is a migrant, wintering at sea in the tropical oceans.

Pomarine Skua (Jaeger) Stercorarius pomarinus

BirdLife Species Account

Pomarine Skua (Jaeger) Stercorarius pomarinus

IUCN Species Status

Pomarine Skua (Jaeger) Stercorarius pomarinus

HBW Species Account

Pomarine Skua (Jaeger) Stercorarius pomarinus

Cornell Species Account

The Pomarine Jaeger is the largest of the jaegers, and the only one that has a bulging and twisted “spoon-shaped” tip to the long central tail feathers; the other two have pointed central tail feathers.

Arctic (Parasitic) Skua (Jaeger) Stercorarius parasiticus

Species Account

The parasitic jaeger (Stercorarius parasiticus), also known as the Arctic skua or parasitic skua, is a seabird in the skua family Stercorariidae. The word "jaeger" is derived from the German word Jäger, meaning "hunter".

Arctic (Parasitic) Skua (Jaeger) Stercorarius parasiticus

BirdLife Species Account

Arctic (Parasitic) Skua (Jaeger) Stercorarius parasiticus

Cornell Species Account

The Parasitic Jaeger is the medium sized of the three jaeger species. It is also as it name implies quite a keen kleptoparasite, and often it focuses on terns as well as smaller gulls when trying to steal food.

Arctic (Parasitic) Skua (Jaeger) Stercorarius parasiticus

Species Account

Sound archive and distribution map.

Long-tailed Skua (Jaeger) Stercorarius longicaudus

RSPB Species Account

The long-tailed skua is a medium-sized seabird and our smallest skua. It is the size of a black-headed gull, with slim wings and long delicate tail streamers.

Long-tailed Skua (Jaeger) Stercorarius longicaudus

BirdLife Species Account

Long-tailed Skua (Jaeger) Stercorarius longicaudus

Species Account

Skuas are strong-flying piratical seabirds allied to gulls. The long-tailed skua is the smallest of the three holarctic-breeding skua species that regularly visit New Zealand.

Long-tailed Skua (Jaeger) Stercorarius longicaudus

HBW Species Account

Long-tailed Skua (Jaeger) Stercorarius longicaudus

Species Account

The long-tailed jaeger (Stercorarius longicaudus), known as the long-tailed skua outside the Americas, is a seabird in the skua family Stercorariidae.

Long-tailed Skua (Jaeger) Stercorarius longicaudus

IUCN Species Status

Long-tailed Skua (Jaeger) Stercorarius longicaudus

Species Account

Sound archive and distribution map.

Number of Species

Number of bird species: 7

Useful Reading

Seabirds

by Peter Harrison - Helm 1985

ISBN: 071363510X

Buy this book from NHBS.com

Seabirds - a natural history

by Anthony J Gaston A&C Black 2004
See Fatbirder Review

ISBN: 0713665572

Buy this book from NHBS.com

Organisations

The Seabird Group

Website

The Seabird Group, a registered charity, was founded in 1966 to promote and help coordinate the study and conservation of seabirds…

Southern Oceans Seabird Study Association

Website

SOSSA was founded by members of the New South Wales Albatross Study Group (NSWASG) in 1994. It was set up to be an umbrella organisation for many study groups concerned with studies of Southern Ocean bio-diversity. SOSSA is a wildlife research and conservation group which consists of dedicated people both professional and amateur. These people share a common interest and concern for the environment and the wildlife of the Southern Oceans…

Other Links

Seabird Osteology

Website

The Seabirds Skull Gallery, existing since 2002, has only been changed a bit and was given a new name that covers the subject more properly. After two years working on this site it is not only skulls anymore that are shown. Regular visitors have already noticed that since December 2004 the scope has widened. It now includes also other parts of the seabird skeleton. In the Seabird Osteology section general aspects of seabird osteology are treated and in the species section you willl find a listing of families and groups with links to pages on skeletons of particular species or groups. There is always work in progress, which means that there will be additions and improvements from time to time…