Bird song syntax: learned intraspecific variation is meaningful.

Song syntax, defined as orderly temporal arrangements of acoustic units within a bird song, is a conspicuous feature of the songs of many species of passerine birds. While syntactical features play a role in interspecific song recognition by males of many bird species, syntax variation within species and female responsiveness to song syntax have received little attention. This report demonstrates that differences in naturally occurring learned song syntax within a species whose syntax varies geographically are behaviorally salient to both male and female birds. The salience of culturally transmitted intraspecific differences in song syntax has implications for the process of conspecific song perception and may be involved in the regulation of genetic exchange between large populations of swamp sparrows (Melospiza georgiana).