Acoustic Communication in the Belted Kingfisher: an Example of Temporal Coding

Abstract

Associations between call structure and function were examined in vocalizations of Ceryle alcyon. Four structural groups were recognized and message content within each group was inferred from the sender's behaviour and context. Both spectral and temporal properties of calls varied within each group. Notably, temporal patterning of pulses covaried with behaviour: calls comprised of doublet patterns were associated with aggressive behaviour of the sender while calls comprised of evenly spaced pulses were not. A summary of message content for each call group is as follows: 1) scream calls were associated with non-aggressive behaviour such as retreat and defensive threat, 2) harsh calls were used by males during intrasexual disputes and when combined with scream calls to attract females, 3) rattle calls were associated with a broad spectrum of behaviour which also included territorial conflicts, and 4) warbling calls were emitted by females when soliciting copulations. In field experiments, the agonistic response of individuals to playback of natural calls was measured. Responses were stronger to scream calls than to harsh calls. In an experiment using structural variants of rattle calls, levels of response across call variants also differed. Because call structure and behaviour covaried, it is proposed that rattle calls form a graded signalling system useful for mediating territorial confrontations.