Arctic Skua: The Avian Pirate of the Seas
The Arctic skua (Stercorarius parasiticus), also known as the parasitic jaeger or parasitic skua, is a seabird that belongs to the skua family Stercorariidae. It is a migratory species that breeds in the northern regions of Eurasia and North America, and winters across the southern hemisphere. It has a reputation as an avian pirate, stealing much of its food from other birds by harassing them in flight until they drop their prey.
The Arctic skua is a medium-sized bird, measuring 41â48 cm (16â19 in) in length, 107â125 cm (42â49 in) in wingspan and weighing 300â650 g (11 oz â 1 lb 7 oz). It has a brown back, dark primary wing feathers with a white “flash”, and mainly white underparts. The head and neck are yellowish-white with a black cap and there is a pointed central tail projection. Some individuals have darker plumage, ranging from brown to black. Juveniles are similar to adults but have more streaks and spots on their plumage.
The Arctic skua is a kleptoparasite, meaning it obtains food by stealing it from other species. It mainly targets terns, puffins, and other seabirds that are carrying fish or other prey back to their nests or young. It attacks them in midair and forces them to drop their food, which it then catches before it falls into the water. It sometimes works in pairs or groups to overwhelm its victims, and it is relentless in chasing them down. It can also hunt for its own food by diving into the water or catching insects and rodents on land.
The Arctic skua breeds in open tundra, moorland, or islands near the coast. It nests on the ground in a shallow scrape lined with vegetation. It lays one to three eggs, which are incubated by both parents for about 24 days. The chicks are fed by both parents and fledge after about 28 days. They remain with their parents until they migrate south in late summer or autumn.
The Arctic skua has a large global population estimated at 380,000 individuals. It is classified as Least Concern by the IUCN Red List of Threatened Species. However, it faces some threats from habitat loss and degradation, human disturbance, predation by invasive species, pollution, and climate change. In Europe, it is considered Endangered due to a steep decline in its breeding population since the 1980s. The main causes of this decline are thought to be reduced availability of food due to overfishing and competition with larger skuas.
- BirdLife International (2020). Stercorarius parasiticus. The IUCN Red List of Threatened Species 2020: e.T22694297A181975233. https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T22694297A181975233.en.
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