The parasitic jaeger feeds using a method of acquiring food known as kleptoparasitism (6). It chases terns, auks or gulls until the fleeing bird is so distressed that it drops any fish it has recently caught, in order to escape from the parasitic jaeger (3). The jaeger promptly eats this illicitly gained meal by catching it in mid-air or from the surface of the water. The genus name for the parasitic jaeger, Stercorarius, means ‘of or belonging to dung’ in Latin, and originates from an old misconception that it was the pursued bird’s excrement which the jaeger seized from the sky (3).
The jaeger is a talented flier, and is able to manoeuvre with great speed in pursuit of its prey (2). It was the very appropriate inspiration for the Blackburn Skua, the British Fleet Air Arm’s first naval dive-bomber (3). This species is also able to fly into high winds by beating its wings very rapidly and constantly shifting to account for buffeting (2).
The parasitic jaeger will also eat small birds, rodents, insects, eggs and berries (6).
In April or May, the parasitic jaeger arrives at its northern breeding areas (6), where it breeds in loose colonies (3). The parasitic jaeger attracts a mate through an elaborate flying display. Some pairs mate together repeatedly year after year, while others may switch to a new partner (6). Eggs are laid in May or June (4), usually in a scrape in the ground lined with some twigs or straw (6). Breeding pairs share the duty of guarding the nest and will attack much larger intruders by diving at them at high speed (3) (6). Immature parasitic jaegers begin to leave the breeding habitat soon after they arrive in July (6), while the breeding adults and fledglings remain until August or September (4).
After the breeding season, the parasitic jaeger will initially follow the coast south, often seeming to follow migrating flocks of Arctic terns (Sterna paradisaea), before moving out to sea (2). Most individuals of this species spend the winter near the coasts of South America and western Africa. Many immature individuals spend their first two years in wintering areas, before returning to the breeding grounds (4).