Parasitic Jaeger

Fascinating facts about the Parasitic Jaeger

• The parasitic jaeger measures 41–48 cm in length and has a wingspan of 107–125 cm.
• A breeding adult’s tail streamer adds about 7 cm to its length.
• When it lays eggs, a female can pack up to four olive-brown eggs into a single clutch on the dry tundra, a surprisingly high number for a bird that spends most of its life at sea.
• First described by Carl Linnaeus in 1758, the species was placed in the genus Stercorarius in 1760.
• Although globally listed as Least Concern, Iceland lifted the bird to Endangered status in 2018 after its numbers nosedived in the early 2000s, a stark reminder that regional threats can outpace global assessments.

At a glance

About the Parasitic Jaeger

The parasitic jaeger (Stercorarius parasiticus), a sleek seabird of the skua family, is small for its kind, measuring 41–48 cm in length with a 107–125 cm wingspan and weighing 300–650 g. Three colour morphs, light, dark, and intermediate, share a striking white wing flash, while breeding adults flaunt a yellow-white head, black cap, and a 7 cm tail streamer that hints at its name’s German root, Jäger, meaning “hunter.” Its flight, more falcon-like than the tern-like long-tailed jaeger, carries it over the stark tundra and high fells where it nests on dry ground, laying up to four olive-brown eggs. On the breeding grounds it supplements its diet with rodents, insects, eggs and chicks, but once the season shifts, the bird becomes a master kleptoparasite, snatching catches from gulls and terns across the open ocean, a behavior that gave rise to its common name. A nasal mewing call punctuates its aerial displays, and an alarm call sharpens when intruders, human or fox, approach the nest, prompting the jaeger to swoop aggressively at the threat. During migration and winter the parasitic jaeger traverses the globe, breeding in northern Fennoscandia, Scotland, Iceland, Greenland, northern Canada, Alaska and Siberia, then wintering across the southern hemisphere’s tropics and southern oceans. Overland routes are a surprise: spring migrants cross Alaska’s Canning River Valley, while Eurasian birds fly from northern Russia to the Persian Gulf and North American birds over the Great Lakes, especially Lake Ontario. This blend of oceanic wandering and occasional terrestrial passages underscores the species’ adaptability, allowing it to exploit a wide range of marine and coastal ecosystems while maintaining its signature kleptoparasitic lifestyle.

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