Barnacle goose loud calls were recorded in a semi-captive flock in Slimbridge. A quantitative analysis of those calls revealed a high degree of individuality in their structure. The duration and fundamental frequency of the calls did not vary much between birds, but the frequency of maximum amplitude did vary from one bird to another. No differences appeared between sexes. Individuality involved complex parameters that required special analysis programs. Frequency spectrum and frequency modulation (obtained by fundamental extraction) were individually distinctive. The combination of these two parameters gives excellent individual distinctiveness and enables 98% correct identification of the calls of individuals.