Temporal Variation of Kelp Gull's (Larus dominicanus) Diet on a Coastal Island of the Rio de la Plata Estuary, Uruguay: Refuse as an Alternative Food Source

Abstract

Temporal variation in the diet of the Kelp Gull in relation to feeding on refuse was studied at a reproductive colony on Isla de las Gaviotas, Uruguay. Diet was assessed temporally within the reproductive season, and inter-annually for 2011 and 2012 reproductive seasons, and the 2013 non-reproductive season. Data analysis was focused on the proportion of the most important diet items recorded in regurgitated pellets: fish and organic refuse. Fish and organic refuse correlated negatively at an intra-monthly scale. Additionally, fish was more frequently recorded during the incubation period (68% of pellets) than during the chick-rearing period (42% of pellets). Conversely, proportion of organic refuse was larger during the chick-rearing period (18% of pellets) than during the incubation period (8% of pellets). During reproduction, fish proportion in diet was larger (2011 = 41% of pellets, 2012 = 32% of pellets) than refuse (2011 = 16% of pellets, 2012 = 15%) and the opposite situation occurred during the non-reproductive season (fish 2013 = 14% of pellets, refuse 2013 = 41% of pellets).