All species › Waders, gulls and terns › Jaegers and skuas › Parasitic Jaeger
Parasitic Jaeger | Stercorarius parasiticus
Kleine jager | Págalo parásito | Mandrião-parasítico
The Parasitic Jaeger is a slender, falcon-like seabird that steals much of its food: it chases terns and small gulls in fast, agile pursuits until they drop their fish. It breeds on tundra and moorland around the North Pole and winters at sea, largely in the southern hemisphere. Of the three small jaegers it is the one that stays closest to the coast in the guide area, where the terns fish.
Voice
Usually silent in the guide area. On the breeding grounds a mewing, plaintive ee-ah; during chases sometimes short, sharp calls.
Recording: Stanislas Wroza — CC BY-NC-SA 4.0 · xeno-canto
Identification
41–48 cm, including the pointed, elongated central tail feathers of the adult, which project 8–14 cm beyond the tail and are often missing during moult. Slim, with narrow, pointed wings and a fairly thin bill. There are pale and dark morphs, with intermediates. The pale morph is greyish brown above, with a dark cap, a white to yellowish neck and white underparts, often with a greyish-brown breast band; the dark morph is entirely dark greyish brown. Both show a white patch at the base of the primaries and three to five white shafts from above. In non-breeding plumage the flanks and rump are barred. Juveniles are barred warm brown to rufous, with pale tips to the primaries and short, pointed central tail feathers. The sexes are alike.
Confusion species
Pomarine Jaeger Stercorarius pomarinus is larger and heavier, with a broader chest, a thicker, two-toned bill and, in adults, broad, twisted central tail feathers with a blunt tip; its flight is slower. Long-tailed Jaeger Stercorarius longicaudus is slimmer, with very long, thin central tail feathers in adults, greyer upperparts with paler wing coverts against dark flight feathers and only two white shafts. Juveniles of the three species are very similar; note structure, bill, colour and the shape of the tail tip. Chilean Skua Stercorarius chilensis is much larger and bulkier, with broad wings and a short tail.
Habitat
In the guide area mainly inshore waters, bays and the zone just beyond the surf, where terns and small gulls fish; less far out to sea than the other small jaegers. It rests on the water and sometimes on beaches and sandbars. It feeds on fish stolen from other seabirds, as well as fish it catches itself and discards from fishing boats. It does not breed in the guide area; the nest is a scrape on tundra or moorland.
Where the bird is most at home, classified by the vegetation units of the Andes and the west coast.
Range and movements
In Peru a fairly common winter visitor and passage migrant along the whole coast, often visible from land. In Ecuador and along the Pacific and Caribbean coasts of Colombia in smaller numbers; scarce in the waters around the Galápagos. Some immatures stay all year. Not in Bolivia. Breeds around the North Pole in North America, Europe and Asia and winters at sea, especially off the coasts of South America, Africa and Australia.
- Resident
- Winter visitor (c. Oct–Mar)
- Passage (Mar–Apr, Oct–Nov)
- dark = core range, pale = thinly spread
How and when to look
Watch from a headland or pier where terns fish in large numbers, for instance at Pucusana or Paracas in Peru; between October and April Parasitic Jaegers often chase them close inshore. Also seen from boats in bays.
Conservation status
Least Concern. Numbers are declining at part of the breeding range; at sea the species depends on terns and fish, which can decrease sharply during El Niño.
Scientific name
Stercorarius parasiticus | (Linnaeus, 1758)
Linnaeus described the species in 1758 as Larus parasiticus; because it was later moved to another genus, the author and year stand in brackets. The genus Stercorarius was introduced in 1760 by Brisson. The genus name is Latin stercorarius, 'of dung' (from stercus, 'dung'); food disgorged by birds chased by skuas was once thought to be excrement. The species name comes from Latin parasiticus (from Greek parasitos, 'one who eats at another's table'), after the habit of stealing food from other seabirds. The specimen the first description was based on came from coast of Sweden.