Perdeck A.C. (1963) The early reproductive behaviour of the Arctic Skua, Stercorarius parasiticus (L.). ARDEA 51 (1): 1-15

A description is given of the reproductive behaviour of the Arctic Skua up to the laying of the eggs. The agonistic behaviour includes two Upright postures, a Long Call and two other calls. Territorial fighting consists of Swoops and a peculiar counterattack to these, the Jump, in which the bird throws itself upside down in the air, kicking up at the swooping bird. Both Swoops and Jumps are carried out also during long Pursuit Flights. During pair formation and precopulatory display regurgitating is common. The introduction to this, the Begging is done by both male and female. Unlike the Great Skua Squeaking is not clearly different from Begging. Pair formation seems to occur on territoria lying between the incubation territories. The behaviour is compared with that of the Great Skua and the relation of some differences with the more aerial habits of the Arctic Skua is discussed. A preliminary comparison is made of the displays of skuas and gulls as groups. Attention is drawn to the poorer repertory of displays in the skuas and to the greater aggressiveness thought to be due to the parasitic feeding habits.