Olrog's Gull Larus atlanticus: specialist or generalist?

Summary A study was made of the feeding behaviour of Olrog’s gull Larus atlanticus in winter.Although feeding mainly on crabs they also, contrary to previous observations, made useof discarded offal, much as other species of gull. Such generalist feeding habits are likelyto be beneficial to the conservation of the species. Introduction Olrog’s Gull Larus atlanticus is considered to have a Vulnerable status (Collar etal. 1994). It is thought to be a specialized predator on crabs (Escalante 1966, 1984,Spivak and Senchez 1992, Yorio and Harris 1992, Burger and Gochfeld 1996) butoccasionally also forages on discarded offal from fishing vessels (Jehl and Rum-boll 1976), mussels Mytilus (Escalante 1966), fish (Olrog 1967) and insects (Spivakand Sa´nchez 1992).During the austral spring Olrog’s Gull breeds in small colonies in Bahi´a Blanca,Bahi´a San Blas and Bahi´a Bustamante (Argentina). Outside the breeding seasonits range extends from Puerto Deseado (Argentina) to Uruguay and southernBrazil (Olrog 1948, Escalante 1984, Yorio and Harris 1992, Collar