Little is known about owl song. We made sonagrams of the territorial calls of 50 male Tawny Owls Strix aluco from three different areas. Six temporal and four frequency measures of the calls were recorded from the sonagrams. The measures of the calls were then subjected to analysis to try to separate between individual owls and between owls from different areas. We also looked for similarities between calls of neighbouring owls and for any effect of habitat on owl hoots. Individual owls were separated on the basis of their hoots with a high degree of success (98.6% overall), and there were significant differences between areas. Differences were found between calls in woodland and farmland habitats, but these differences were not in the direction expected to increase sound transmission. Calls of neighbouring owls did not resemble each other more than calls from owls that were not in vocal contact, implying that if calls are learned by Tawny Owls, they are learned before dispersal.