Abstract

The diet of Burrowing owl (Athene cunicularia) was analyzed in four islands in the North of Chile, showing that a strong predominance of arthropods (89.1%) exists compared to vertebrates (10.1%) regard to the number of consumed preys. Tenebrionids (42.2%) and curculionids (31.2%) stand out because they are the main consumed groups. However, the presence of mammals (3.6%) and birds (6%) in the diet is relevant too, because despite representing less than 10% of the total number of prey, the energy contribution of vertebrates constituted about 80% of the total biomass ingested. Evidence of predation on Peruvian diving petrel (Pelecanoides garnotii) was found, this prey stands out with 71% from the birds group, while regarding the total consumed vertebrates it reaches a 40%. It is also worth mentioning the mouse-opossum (Thylamys elegans) consumption reaching 21% of the total vertebrates. Three individuals of Piuchen or vampire bat (Desmodus rotundus) were observed, this species have not been previously described in the Burrowing owl diet in the North of Chile. We discuss possibles functional and numerical responses of Burrowing owl in Choros Island, where different densities of Peruvian diving petrel were found. Besides, the diet variability per island, pattern size of preys consumed and spatial distribution of Burrowing owl nests were analyzed.