About Stercorarius longicaudus Vieillot, 1819
Adult Stercorarius longicaudus are easy to identify, with a grey back, dark primary wing feathers that lack a white "flash", a black cap, and a very long tail. Adults often hover over their breeding territories. Juveniles are far harder to identify, and are difficult to distinguish from parasitic jaegers when out at sea. Compared to parasitic jaegers, juvenile Stercorarius longicaudus are slimmer, have longer wings, and have a more tern-like shape, while sharing the same wide range of plumage variation. They are usually colder in tone than parasitic jaegers, with greyer shades rather than brown. This species is the smallest in the skua family, with a total length ranging from 38 to 58 cm (15 to 23 in) that varies by season and age. Up to 29 cm (11 in) of this total length comes from the tail; summer adults have tail streamers that can measure up to 15 cm (5.9 in). This species has a wingspan ranging from 102 to 117 cm (40 to 46 in) and a body mass ranging from 230 to 444 g (8.1 to 15.7 oz).
