The Parasitic Jaeger (Stercorarius parasiticus) is a seabird whose name perfectly captures its survival strategy. A true pirate of the air, it gets its name from its behavior of kleptoparasitism: it pursues and harasses other birds, such as terns, gulls, and puffins, until they drop or regurgitate their meal, which it then snatches in mid-air. Agile and fast, its flight resembles that of a falcon, and its chases are both an impressive and ruthless spectacle.
By the Les-Oiseaux.com team, published on July 29, 2025
My advice: To see the Parasitic Jaeger in action, position yourself on a headland or rocky point during migration periods (April-May and August-September). Look for gatherings of actively fishing terns or gulls. That's where the pirate waits for its moment.
The show often begins with a sudden panic within the group. Spot a dark, swift bird swooping down on a victim. The pursuit is relentless, full of dives and sharp turns, until the harassed bird gives up its catch. Observing this behavior is to understand the very essence of the Parasitic Jaeger. It's one of the most captivating dramas of coastal bird life.
Identifying the Parasitic Jaeger is complex due to the existence of several plumage morphs (phases) and its resemblance to other jaegers. It has a slender build with long, pointed wings.
| Characteristic | Male | Female | Record / Average |
|---|---|---|---|
| Length | 37 – 53 cm | 37 – 53 cm | Up to 53 cm (including tail) |
| Weight | 380 – 420 g | 460 – 510 g | 300 – 650 g |
| Wingspan | 107 – 125 cm | 107 – 125 cm | Up to 125 cm |
| Flight Speed | Not specified | Not specified | Up to 80 km/h (when chasing) |
| Lifespan | Not specified | Not specified | Over 30 years (banded individual) |
In the North Atlantic, the Parasitic Jaeger can be confused with the Great Skua (Stercorarius skua), another sea pirate. However, their size and structure are key clues for differentiation.
Tip: Focus on the overall silhouette and flight style. The Parasitic Jaeger is a slender and agile "fighter," while the Great Skua is a stocky and powerful "brute." If you see long, pointed tail streamers, it's an adult Parasitic Jaeger.
The Parasitic Jaeger is generally a silent bird, especially away from its breeding grounds. On the tundra, it becomes more vocal and can produce a variety of calls. The most common is a plaintive, nasal, cat-like cry, a long, drawn-out "yeeoo-arr." When defending the nest, it may also utter shorter alarm calls.
The Parasitic Jaeger leads a double life. During the breeding season (from May to August), it settles on land, in the Arctic tundra, coastal moorlands, and barren islands. It is a circumpolar breeder, found across northern Eurasia and North America.
Outside of this period, it is a pelagic bird that winters at sea, mainly in the oceans of the Southern Hemisphere, but generally staying along the coasts. It is a transequatorial migrant.
The diet of the Parasitic Jaeger varies radically with the season.
At sea and during migration, it gets most of its resources from kleptoparasitism. It aggressively chases terns, gulls, and other seabirds to force them to give up their catch, which it skillfully grabs before it hits the water. It also takes advantage of fish discards from fishing boats.
On its breeding grounds in the tundra, it becomes an active predator. It then feeds on small rodents like lemmings and voles, eggs, chicks, small birds, insects, and even berries.
The Parasitic Jaeger nests in solitary pairs or loose colonies on the tundra. The nest is a simple scrape in the ground, sometimes lined with a few grasses or lichens. The female typically lays 1 to 2 eggs (rarely up to 4), which are olive-brown with dark spots. Both parents participate in incubation, which lasts about 26 days, and in raising the young. They are extremely aggressive in defending their nest, not hesitating to dive-bomb and strike intruders, including humans, with their feet and bill.
Its name comes from its behavior of kleptoparasitism (from the Greek 'kleptes', meaning 'thief'). It harasses other seabirds, such as terns or gulls, in mid-air to make them regurgitate or drop their catch, which it then snatches with disconcerting agility. It is the quintessential pirate of the seas.
The Parasitic Jaeger does not nest in the contiguous United States, but it can be observed during its migrations along the coasts. It is a circumpolar breeder in the Arctic and winters at sea, primarily in the Southern Hemisphere.
No, the Parasitic Jaeger is currently listed as 'Least Concern' (LC) by the IUCN. However, like many seabirds, its populations can be affected by climate change, which impacts the availability of its prey in both the tundra and the oceans.