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Jan 16 2011

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Arctic Skua (Stercorarius parasiticus)

Arctic Skua

Charadriiformes Stercorariidae Arctic Skua (Stercorarius parasiticus)

[order] Charadriiformes | [family] Stercorariidae | [latin] Stercorarius parasiticus | [UK] Arctic Skua | [FR] Labbe parasite | [DE] Schmarotzerraubmöwe | [ES] Págalo Parásito | [IT] Labbo | [NL] Kleine Jager

Physical charateristics

The Parasitic Jaeger (known in most of the world as the Arctic Skua) is medium in size between the smaller Long-tailed Jaeger and larger Pomarine Jaeger. Its plumage is highly variable, with light, intermediate, and dark morphs. Light morphs have brown upperparts with a blackish cap and white collar, white underparts, and yellowish sides of the neck. They often have a partial or complete breast band. Dark morphs have brown underparts and head. All morphs have a white patch on the underwing and pointed central tail feathers that extend beyond the rest of the tail. These long tail feathers are lost during the non-breeding season. Juvenile and immature plumage also varies from light to dark. In general, except for dark morphs, juveniles and immatures have an orangish-brown or cinnamon wash on the head and neck, and barring on the back.
They are often seen in association with flocks of small gulls and terns. Parasitic Jaegers are agile in flight, and they often forage by chasing other seabirds and forcing them to drop their prey (kleptoparasitism). Breeding pairs defend large territories where they often cooperate in hunting birds, eggs, and rodents. On breeding grounds where the primary source of food is kleptoparasitism, territories are small and pairs nest in loose colonies.

wingspan min.: 108 cm wingspan max.: 118 cm
size min.: 37 cm size max.: 44 cm
incubation min.: 25 days incubation max.: 28 days
fledging min.: 25 days fledging max.: 30 days
broods: 1   eggs min.: 1  
      eggs max.: 3  

Distribution

Stercorarius parasiticus is a widespread breeder in coastal areas of northern Europe,
which accounts for less than a quarter of its global breeding range. Its European
breeding population is relatively small (<140,000 pairs), but was stable between 1970- 1990. Although the species declined in Norway, Svalbard and the United Kingdom during 1990-2000, trend data were not available for key populations in Greenland, Iceland and Russia, and there is no evidence to suggest that the species declined significantly overall.

Listen to the sound of Arctic Skua



Copyright remark: Most sounds derived from xeno-canto

Habitat

During migration, Parasitic Jaegers are more often found near shore and in estuaries than other jaegers. They spend most of the year on the ocean within a few miles of land. They nest on Arctic tundra, often near a body of water.

Foraging habits

During the breeding season they eat a variety of birds and their eggs, rodents, insects, and berries. Non-breeders eat mostly fish stolen from other birds. Parasitic Jaegers are less dependent on lemming populations than are other jaegers


copyright youtube

Breeding habits

Pairs usually return to the same territory each year. Males tend to arrive earlier to reclaim territory. The male chooses the nest site, which is often on a slight rise away from cover. The female builds the nest, a shallow depression sometimes lined with grass or lichens. Both sexes share incubation of the 2 eggs. The young may leave the nest within 2 days after hatching, but remain nearby. The parents feed the young by regurgitating food. The young stay with their parents for a few weeks after fledging, which occurs at 25-30 days.

Conservation

This species has a large range, with an estimated global Extent of Occurrence of 10,000,000 km². It has a large global population estimated to be 500,000-1,000,000 individuals (del Hoyo et al. 1996). Global population trends have not been quantified, but populations appear to be stable (del Hoyo et al. 1996) so the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern. (source Birdlife.org)

Arctic Skua status Least Concern

Migration

Migratory; pelagic away from breeding areas. In Atlantic, individuals occasionally seen in winter as far north as British Isles; but great majority of all age-classes are transequatorial migrants which winter mainly on Patagonian Shelf off Argentina, and in Benguela Current off Namibia and South Africa.
Leaves breeding grounds early August and immediately begins dispersal in general southerly direction, with many Scottish birds entering North Sea where terns more numerous than on Atlantic coast. Leisurely passage through north-temperate seas lasts well into October. Rapid return movement begins April, at peak over Atlantic in early May when there are pelagic records from Equator to breeding latitudes. Adults begin arriving Scottish colonies in late April though up to 3 weeks later further north and east.

Distribution map breeding season

Arctic Skua range map summer

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Permanent link to this article: http://www.planetofbirds.com/charadriiformes-stercorariidae-arctic-skua-stercorarius-parasiticus

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