On Bonaire we assessed Bam Owl Tyto alba diets at four discrete sites. The 233 fresh pellets contained 755 identifiable prey items from four taxonomic orders. Average prey diversity differed two- to threefold between sites. Dietary composition showed large spatial variations between sites, from predominantly insectivorous to avian. Between-island variation was assessed by comparing the dietary composition of populations of Barn Owls on nine islands throughout the Caribbean region as reported in the literature. On 8/9 islands mammals (mainly rodents and bats) formed the main diet. On half of the islands about a fifth or more of the prey comprised birds. Reptiles and/or insects were eaten on 5/9 islands, but rarely dominated the diet. These large within-island dietary differences reflect differential prey availabilities in the Caribbean, possibly enhanced locally by specialisation.