Kelp Gull predation on an Imperial cormorant colony in Patagonia

QUINTANA, F.; YORIO, P.

Marine Ornithology

Año: 1998 vol. 26 p. 84 - 85

Gulls breeding in mixed-species assemblages can adversely affect many species through egg or chick predation, kleptoparasitism and breeding site competition (e.g. Thomas 1972, Bourget 1973, Becker 1984, Furness 1987, Furness & Monaghan 1987). At the Punta León seabird colony, Chubut, Argentina, Kelp Gulls Larus dominicanus breed adjacent to a large colony (2669 and 2658 pairs for 1989 and 1990, respectively) of Imperial Cormorants Phalacrocorax atriceps (both atriceps and albiventer colour morphs, sensu Rasmussen 1991). At this mixed-species colony, the Kelp Gull is the most abundant breeding species, has increased in numbers during the last 10 years from 3664 in 1982 to 6500 breeding pairs in 1995 (Malacalza 1987, Yorio et al. 1998), and has been previously reported to prey upon cormorant eggs and young (Malacalza 1987). As part of a broader study of the ecological interactions between Kelp Gulls and other seabirds at Punta León, we evaluated the impact of gull predation on the cormorantcolony. In this paper we present information on predation attempts and predator and antipredator behaviour obtained during the 1989 and 1990 breeding seasons.