Kelp Gull Larus dominicanus predation on an Imperial Cormorant Phalacrocorax atriceps colony in Patagonia

QUINTANA, F.; YORIO, P.

Marine Ornithology

African Seabird Group

Lugar: Ciudad del Cabo; Año: 1998 vol. 26 p. 84 - 85

1018-3337

We evaluated the impact of Kelp Gulls predation on the Imperial Cormorants at Punta León during the 1989 and 1990 breeding seasons. Of a total of 35 observation hours from 28 October 1989 to 2 January 1990, covering both the incubation and chick stages, we observed only one chick preyed upon out of five predation attempts. From 23 October to 20 December 1990 we conducted a total of 87 observation hours, 60 during the egg stage and 27 during the chick stage. During the egg stage we recorded eight predation attempts, seven of which were successful, whereas during the chick stage we recorded 17 predation attempts, 14 of which were successful. Except for one failed attempt when a peripheral gull walked up to a central nest, all successful and unsuccessful attempts were on peripheral nests. Kelp Gulls preyed almost exclusively from the ground by walking up to cormorant nests. All observed predation attempts were by adult Kelp Gulls which either had a nest near the cormorant colony edge or defended territories around this colony. Kelp Gulls do not appear to have a significant impact through predation on the breeding success of Imperial Cormorants at Punta León. Predatory behaviour was restricted to relatively few gulls nesting at the periphery of the cormorant colony, suggesting that an expansion of the Kelp Gull population at Punta León might not necessarily result in a proportional increase in predation rate.