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
María Fernanda Burgues, Javier Lenzi, Emanuel Machín, Lucía Genta, Franco Teixeira de Mello
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).