Light flash stimulation alters the nightingale's singing style: Implications for song control mechanisms

To investigate decision processes during song performances in a species with a large repertoire and a versatile singing style we studied the characteristics of brief song interruptions in male nightingales Luscinia megarhynchos. Interruptions were induced experimentally by exposure to single light flashes. (1) The temporal positioning of stimuli within songs had no clear effect on the likelihood of a song interruption. (2) The delay between stimulus presentation and song interruption showed considerable variation. (3) Song types exposed to the stimulus were repeated significantly more often than in normal singing bouts. (4) In day time singing, durations of silent intersong intervals were not affected by stimulus presentations. During nocturnal singing however silent intersong intervals increased in duration after stimulus presentations unless a song type repetition was following subsequently. The results suggest a mechanism facilitating song type repetitions for songs that were disturbed during singing performance. Whether or not temporal control is affected seems to depend on both time of day and on whether or not a song is repeated after a stimulus presentation.