Spatial and Temporal Patterns in the Diet of the Kelp Gull in Patagonia

Abstract

The Kelp Gull (Larus dominicanus) is an abundant and widely distributed species in coastal Patagonia, and has increased in number at many locations during the last decade. We present comparative information on diet composition between locations and diet variation throughout the breeding cycle at three Provincial Wildlife Reserves (Punta Pirámide, Punta León, and Punta Tombo), Chubut, Patagonia. We analyzed diet using regurgitated pellets. A total of 41 types of prey were identified at the three colonies. Kelp Gulls fed throughout the season mostly on intertidal invertebrates, although fish also was an important diet component, mainly during the chick stage. The diet also included garbage, insects, and other seabird offspring. Of all types of prey, 70.7% were common to the three locations, although the pattern of consumption of the main food categories differed among locations. The average consumption of garbage differed significantly among locations, with larger amounts of garbage in the diet the closer the colony to the nearest landfill. Kelp Gulls showed a marked seasonal variation in the consumption of the main food types. At Punta Tombo and Punta León, there was a change from a mostly marine invertebrate diet during the pre-laying and incubation stages to a mainly fish diet during the chick stage. The consumption of the main food categories was significantly different between seasons at Punta Pirámid but was similar at the other two colonies.