Little Tern (Sterna antillarum) Science Article 1
abstract
Playback experiments performed in a colony of Least Terns near Fort Macon, North Carolina, demonstrated that adults can distinguish the call of their mate from that of a stranger. Sonagram analysis of the ‘Purrit-tit-tit’ call, the most common vocalization used when an adult approaches its mate, revealed that both temporal and spectral characteristics of the first note of the call varied significantly among individuals, whereas all measured features of the second note were not significantly different for different birds. Presumably the first note is used to convey an individual’s identity, while the second note indicates a tendency to approach the mate and perform certain courtship behaviors
Lynn J. Moseley, The Auk 96: 31-39, 1979