Ardea
Official journal of the Netherlands Ornithologists' Union

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Spellenberg I.F. (1971) Breeding behaviour of the McCormick skua Catharacta maccormicki in Antarctica. ARDEA 59 (3-4): 189-230
Behaviour of the South Polar Skua Catharacta maccormicki was studied during the three austral summers of 1963/1964, 1964/1965, 1965/1966 at Cape Royds, Ross Island, and Antarctica. A description is given of the non-aggressive behaviour, the aggressive behaviour, pair behaviour, nesting and incubation of the adults. The behaviour of chicks to fledging age is also described. Breeding territories were generally 1,600 sq. metres in area and between 7-20 territories formed a colony. Communal gathering places on the edges of lakes were present and clubs were also found. Aggressive behaviour consisted of gull-like postures such as Uprights, Long Call Complexes, Bent Necks, Obliques and Wing Raising. Some quantitative observations were made from a limited number of records of territory conflicts and the relative strengths of the postures and calls are discussed. During pair formation and pre-copulatory displays the male frequently gave Aggressive Uprights and the female responded with the Intimidated Upright and the Hunched Posture. Regurgitation by the male was common and generally copulation did not take place until Courtship Feeding was completed. A quantitative analysis is made of the behaviour sequences during pair formation in the clubs and in the breeding colonies. There was some evidence to show that some form of Collecting Trip may exist and that Sideways Nest Building may be present. A Squeaking ceremony was found during pair formation (in clubs and colonies) and prior to egg laying which fixed the scoop used later for laying. Chicks have a repertoire of behaviour comparable to adult behaviour which begins to develop two days after hatching. The chicks were generally aggressive towards each other and fights frequently broke out between sibling chicks often resulting in the death of one of the chicks. The behaviour of the chicks is discussed in relation to the adult calls and postures as well as to the behaviour of jaeger and skua chick behaviour.


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