| Arctic Skua | |
|---|---|
 light morph | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Charadriiformes |
| Family: | Stercorariidae |
| Genus: | Stercorarius |
| Species: | Stercorarius parasiticus |
The Arctic Skua (Stercorarius parasiticus), as it is known in Europe, or Parasitic Jaeger, as it is known in North America, is a seabird in the family Stercorariidae.
Description[]
| Measurements | |
|---|---|
| Length: | 37-44 cm (14.5-17.3 in) |
| Weight: | 450 g (16 oz) |
| Wingspan: | 100-120 cm (39-47 in) |
The Arctic Skua is one of the smaller and more slender species of skua, being larger only than the Long-tailed Skua. It has an overall dainty, elegant appearance, with long wings, a relatively small head, and a small, although hooked, bill. Despite being similar to the other skuas, this bird can be identified thanks to its central tail streamers, which despite being up to 8 cm long in the breeding plumage are still shorter than the Long-tailed Skua's, and are pointed rather than spoon-shaped like the Pomarine Skua's. Adults come in two colour morphs, one dark and one light. The light phase is greyish-brown above and whitish below, with a grey band across the chest, dark wings and tail, and a black cap. The dark phase is almost completely solid brown, but the cap usually still appears darker. Both morphs have a faint pale patch at the base of the primaries, as well as dark legs and bill. The juvenile has shorter tail streamers and is warm brown in colour with heavy mottling all over its body. Like the adult, it also has a pale wing patch. All skua species display reverse sexual dimorphism, with the female being slightly larger than the male.
Voice[]
This bird's calls are usually only heard at the nesting site. The most common are a sharp, nasal "ee-err", a loud "kek-kek", and a high-pitched "tik-a-tik", as well as various mewing sounds, often given in a sequence.
Behaviour[]
Dark morph
Like all skuas, this species is opportunistic and aggressive, both towards its victims and towards potential predators threatening its nest or young, such as foxes. The shape of its wings and tail makes it quick and agile, appearing almost falcon-like in flight.
The Arctic Skua reaches sexual maturity at 3-4 years of age, and may live up to 18 years.
Feeding[]
During the breeding season, the Arctic Skua feeds on small mammals, nestlings, eggs, carrion, fish, and invertebrates. It obtains much of its food through kleptoparasitism, usually targeting terns, small gulls such as the Kittiwake, and auks. It ambushes seabirds as they return to their colonies with food for their young, chases them in flight, and eventually hits them in mid-air, forcing them to drop their catch. In winter, the Skua is mostly piscivorous and usually hunts its own food.
Breeding[]
Adult incubating
The Arctic Skua is monogamous and generally nests in isolated couples. These skuas tend to seek out partners of the opposite colour morph, ensuring that phases are continuously passed down from one generation to the next. The courtship display takes place in May, at the beginning of the breeding season, and has the two birds performing acrobatic aerial maneuvers before swooping to the ground, where they face eachother as they beat their wings and make nasal calls. The pair nests on the ground, in a depression surrounded by low vegetation. The female lays a single annual clutch of two (sometimes one) olive-coloured eggs with dark spots, which the parents take turns incubating for 24-28 days. The young are semi-nidiculous, leaving the nest after a few days but remaining in their parents' territory. They learn to fly at about 30 days of life, and become fully independent at 7-8 weeks.
Distribution and habitat[]
This bird breeds in tundras and open coastal areas in the arctic and sub-arctic regions of northern Eurasia and North America. A migratory species, it winters on the open sea, reaching the oceans of the Southern Hemisphere.