long-tailed skua

long-tailed skua
Name	Long-tailed skua
Status	LC
Status system	IUCN3.1
Genus	Stercorarius
Species	longicaudus
Authority	(Vieillot, 1819)

long-tailed skua is a medium-sized seabird in the family Stercorariidae, known for its elegant, elongated central tail feathers. It breeds on the Arctic tundra of North America, Eurasia, and Greenland, and undertakes a remarkable trans-equatorial migration to winter in the Southern Ocean. This agile predator and kleptoparasite is closely related to other skua species like the parasitic jaeger and the pomarine jaeger.

Description and taxonomy

The long-tailed skua was formally described by the French ornithologist Louis Pierre Vieillot in 1819. It is placed in the genus Stercorarius with other jaegers, and its specific name longicaudus is Latin for "long-tailed." In breeding plumage, adults have a distinctive black cap, pale greyish upperparts, and white underparts, with the namesake tail streamers extending up to 20 cm. Its flight is notably buoyant and tern-like, differing from its heavier relatives. The species exhibits polymorphism, with pale and dark morphs, though the pale morph is by far the most common. Juveniles are more uniformly brown with barred underparts and lack the elongated tail feathers.

Distribution and habitat

The long-tailed skua has a circumpolar breeding distribution across the high Arctic. Key breeding grounds include the northern coasts of Scandinavia, the Russian Arctic archipelagos like Novaya Zemlya, the Canadian Arctic Archipelago, and the tundra of Alaska and Siberia. Outside the breeding season, it is entirely pelagic, migrating across the Atlantic Ocean and Pacific Ocean to spend the austral summer in cold, productive waters near Antarctica, often as far south as the Antarctic Convergence. On its breeding grounds, it favors dry, open tundra, often near lemming colonies, while at sea it frequents upwelling zones rich in marine life.

Behavior and ecology

This species is highly aerial and migratory, covering vast distances between its Arctic breeding and Antarctic wintering grounds. It is known for its aggressive defense of nesting territories, often dive-bombing intruders like the Arctic fox or humans. Long-tailed skuas are social, often seen in loose flocks during migration and on wintering grounds. A key aspect of their ecology is their population dynamics' tight linkage to the cyclical abundance of their primary prey, lemmings, in the tundra ecosystem. Their migration routes are among the longest of any bird, with some individuals traveling from Greenland to waters off South Africa.

Diet and feeding

The diet of the long-tailed skua is highly variable by season and location. On breeding grounds, it primarily feeds on small mammals, especially lemmings and voles, and also takes birds, eggs, and insects. This dietary specialization makes its breeding success strongly dependent on lemming population cycles. At sea, it switches to a diet of small fish, krill, and other marine invertebrates, often obtained by surface-seizing. It is an adept kleptoparasite, frequently harassing smaller seabirds like terns and phalaropes to steal their catches, a behavior shared with the parasitic jaeger.

Reproduction and life cycle

Breeding occurs in loose colonies on the open tundra from June to August. The nest is a simple scrape on the ground, often on a raised hummock. The female typically lays two olive-brown eggs, which are incubated by both parents for about 23-25 days. Chick rearing is synchronized with the peak abundance of lemmings. Both parents feed the chicks, which are precocial and leave the nest within days, fledging after approximately 25-30 days. Breeding is frequently skipped in years of low lemming populations. The species exhibits high fidelity to breeding sites, often returning to the same region of the Arctic tundra.

Conservation status

The long-tailed skua is classified as Least Concern on the IUCN Red List due to its extremely large range and population. However, its specialized Arctic breeding ecology makes it potentially vulnerable to the effects of climate change, such as altered lemming cycles and habitat modification on the tundra. Potential threats on migration and wintering grounds include bycatch in fisheries and pollution. It is listed under Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA), and key breeding areas are protected within reserves like the Northeast Greenland National Park.

Category:Skuas Category:Birds of the Arctic Category:Birds described in 1819