LIGHT FLASH STIMULATION ALTERS THE NIGHTINGALES SINGING STYLE - IMPLICATIONS FOR SONG CONTROL MECHANISMS

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