Honest advertisement of pairing status: evidence from a tropical resident wood-warbler

Abstract

This paper reports the first investigation of the mate attraction function of song in a tropical resident wood-warbler. Male Adelaide’s warblers, Dendroica adelaidae(Emberizidae: Parulinae), which sing two categories of song (A and B), maintain territories and monogamous pair bonds year-round. Males that were naturally or experimentally unpaired delivered A songs at significantly higher rates than did paired males during both breeding and non-breeding periods. In contrast, use of B songs and singing at dawn did not vary with pairing status. The dawn chorus, characterized by intense and versatile displays of the B song category by neighbouring males, was absent from the non-breeding season. Dawn singing and the B song category thus appear relatively unimportant in mate attraction in this species. Results are consistent with the hypothesis that the A song category functions in mate attraction in wood-warblers. Furthermore, data from the non-breeding season show that the mate attraction function of song is not narrowly tied to the breeding season in a resident species. These data provide evidence for honest signalling of male pairing status in a socially monogamous species. Throughout the year, male Adelaide’s warblers reveal their pairing status honestly, with a comparatively higher rate of A song delivery signalling that a male is unpaired. Paired and unpaired males were distinguishable based on their singing behaviour. Honest advertisement of pairing status may have been favoured in this species by female defence of mates and a habitat saturated with territories, which would limit opportunities for polygyny or polyterritoriality.