Messages encoded in the songs of chestnut-sided warblers

Chestnut-sided warbler, Dendroica pensylvanica, song repertoires contain two distinct categories of songs, accented-ending and unaccented-ending, which differ in patterns of geographical variation, mode of development and circumstances of use. To determine whether the song categories also differ in the information they make available to listeners, a multivariate model of associations between song category and social and environmental factors was derived from two large samples of singing behaviour. The model showed that song categories encode information about a singer's location, immediate social situation and behavioural tendencies. Accented-ending songs were connected to unmated status, interaction with females and stationary singing in territory centers, but unaccented-ending songs were associated with singing near territorial borders or other males and with tendencies to move and/or fight. The predictive power of song category was not absolute. Instead, each song category encoded a set of behavioural possibilities. More specific messages are probably encoded in finer-level signal variation. (C) 1996 The Association for the Study of Animal Behaviour