In 1974-1975, 34 adult South Polar Skuas Catharacta maccormicki were colour-ringed on 18 nest territories at Bonaparte Point, Anvers Island, near Palmer Station along the Antarctic Peninsula. Subsequently, the area was searched for these birds during the austral summers of 1975-1976 to 1984-1985 and in 1987-1988 and 1989-1990. Fifty-three percent were seen in 1984-1985, 32% in 1987-1988 and 21% in 1989-1990. Annual survival rate averaged 95% from 1974-1975 to 1984-1985; no sexual differences were detected (n = 28 of known sex). Strong territory and mate fidelity were apparent; 34 skuas averaged 1.1 nest territories and 1.7 mates each in 16 years. Only 4 of 34 individuals (all females) were known to change territories, and each territory change involved a change of mates. Although males showed higher territory fidelity than females (P < 0.01), most females (four of five) retained their territories when previous mates failed to return. Seventeen of 34 birds changed mates a total of 24 times; at least 20 mate changes followed the death or disappearance of the former mate. Males showed slightly higher mate fidelity than females (P < 0.04). Female South Polar and Brown Skuas Catharacta lonnbergi did not differ in territory or mate fidelity. From 1974-1975 to 1984-1985, 120 South Polar Skua chicks were ringed on 18 nest territories on Bonaparte Point; 17 were resighted in the Palmer area when they were 3-10 years old. All 17 returnees were found within 3 km of their natal nest sites, and four of them occupied nest territories on Bonaparte Point.
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Survival, site and mate fidelity in south polar skuas Catharacta maccormicki at Anvers Island, Antarctica