Information about behaviour provided by Louisiana waterthrush,Seiurus motacilla (Parulinae), songs

Abstract

The Louisiana waterthrush has two main song forms, termed the primary and extended songs. Each has distinctive behavioural correlates. A flexible interactive playback procedure was used that is especially suited for investigating how the different songs uttered by birds responding to a simulated territorial intruder inform about the singer's behaviour. Subjects that approached in response to playback of either song form sang mostly extended songs. All uttered their longest extended songs in correlation with approach flights. In contrast, before playback, subjects that were not near other waterthrushes sang predominantly primary songs. Naturalistic observations of the subjects and other individuals support the distinction between the behavioural correlates of the two song forms. These observations also suggest that, when singing primary songs and incomplete variants of primary songs, individuals less actively approach or seek out other birds. To facilitate comparisons between species, such singers can be described as taking less initiative to interact. The results of this study, the first using these interactive playback procedures on an oscine species, are comparable to those previously obtained with three species of suboscine tyrannid flycatchers. This similarity suggests that providing information about the extent to which a singer will take the initiative to interact, by approaching or seeking out other birds, may be a widespread property of songs.