In the abandoned quarry of San Carlos (Ibiza, Balearics) prey remains of the barn owl were collected. A total of 6,977 identifiable bone remains from 2,767 individuals of mammals, birds, reptiles and amphibians was found. The spectrum of mammals clearly shows two main prey groups: mice (Mus domesticus, M. spretus : 39.4 %) and shrews (Crocidura russula, C. suaveolens : 38.4 %). Voles, which in continental Europe are the owl’s most numerous prey, are absent on Ibiza; these were replaced by mice and shrews. The record of the Pityusic wall lizard Podarcis pityusensis in the prey remains (0.5%) is remarkable. Obviously, the periods of activity of lizard and barn owl do not ordinarily overlap. One possible explanation might be that due to low prey density, Tyto alba probably starts hunting earlier during summer with its shorter nights. A skull of the European free-tailed bat (Tadarida teniotis) was recorded from the sediment, definitely confirming this species for the first time on Ibiza.