For much of the year, the parasitic jaeger (Stercorarius parasiticus) lives on the move. Known in Icelandic as kjói, this agile seabird’s migrations reach from Iceland’s sand barrens to remote southern oceans, marking it as one of the world’s most widespread and unpredictable skuas.
A landscape shaped by flight
Arriving in Iceland in early May, the parasitic jaeger selects varied habitats for nesting. It prefers sparsely vegetated expanses close to the coast and is often found as high as 700 metres above sea level. During the brief summer months, the bird is common throughout the country, with estimates of 5,000 to 10,000 breeding pairs, a familiar sight for those traversing Iceland’s coasts and open landscapes.
Nesting occurs on dry tundra, high fells, and islands, where clutches can include up to four olive-brown eggs. The parasitic jaeger is normally silent outside the breeding season but fills the nesting grounds with mewing and wailing notes. This secrecy shatters rapidly when the nest is threatened; like other skuas, it is famously bold and will dive at intruders, human or animal alike.
Masters of kleptoparasitism
Perhaps most intriguing is this bird’s feeding method, which has given it both its common and scientific names. While it does hunt rodents, insects, eggs, chicks, and small birds during the breeding season, the bulk of its diet is acquired through kleptoparasitism, robbing other birds of their catches. The Latin genus name Stercorarius once assumed disgorged food was dung, while ‘parasiticus’ directly references its parasitic behaviour. Its English name ‘jaeger’ comes from the German word for hunter.
In action, the parasitic jaeger chases seabirds such as gulls and terns, harassing them until they give up their hard-won prey. This behaviour can be witnessed throughout Iceland, especially during migration and winter. The bird’s flight, described as more falcon-like than tern-like, helps it excel in these high-speed aerial pursuits.
There is variety even within the species’ appearance. The parasitic jaeger is small for a skua, reaching about 45 centimetres in length with a wingspan around 120 centimetres. Its three colour morphs, light, intermediate, and dark, add to its identification challenges. All share a characteristic white flash on the wing.
Though the parasitic jaeger is the most often seen jaeger from Iceland’s shores, it is not alone. Occasional visits from the pomarine jaeger (Stercorarius pomarinus) and small numbers of nesting long-tailed jaegers (Stercorarius longicaudus) bring further variety to Icelandic skies.
Despite its resourcefulness, conservationists in Iceland have noticed troubling trends. Once considered of Least Concern, the species was uplisted to Endangered in Iceland in 2018, following marked population declines earlier that decade. Globally, however, it remains classified as Least Concern.
Sources
- Wikipedia
- Wikipedia (Icelandic) in Icelandic
