Definition in Biology: The Case of "Bird Song"

Unrecognized different definitions for the same term can produce confusion among workers in a field. A review of over 80 definitions of bird song shows little agreement as to what defines bird song or differentiates it from calls. Defining criteria have included structural (e.g. duration), delivery (e.g. rhythmic production), physiological (e.g. hormonal control), developmental (e.g. learning), functional (e.g. territoriality), affecftive (e.g. musicality), and taxonomic (e.g. restriction to passerines) attributes of song. Each criterion has been rejected by some authors. Song definitions often are qualified with exceptions and include such qualifters as "largely arbitrary", "unclear", "not very precise", etc. Song concepts have changed over time and will continue to do so. A single song definition that covers all extant song concepts is not possible. The various song concepts serve different purposes and will be most useful if kept distinct and appropriately labeled.