Abstract
The trill elements of many bird species’ songs have been hypothesized as honest signals of performance. However, the breadth of receiver responses to variation in the signaller’s trill performance is unknown. We exposed wild male Lincoln’s sparrows ( Melospiza lincolnii ) to two song treatments, one with low- and another with high-performance trills. We found no effect of treatment on measures of agonistic behaviour and song length. However, relative to the subjects’ trills following the high-performance treatment, those following the low-performance treatment were elevated in performance due to trill types with high frequency bandwidth in the third trill of songs. Treatment also affected trill duration through its syllable count in a manner that varied by the song’s trill number. Thus, the performance of a signal to which a receiver is exposed drives plasticity in his own performance in sequence-specific manner. Males may showcase their own performance in the presence of lower-performing rivals.