Song variation between sexes and among subspecies of New Zealand Fantail (Rhipidura fuliginosa)

Abstract

ABSTRACT Variation in bird song occurs at many levels, including between sexes and among geographic regions. Variation can be due to differences in function, habitat, selection or drift. Quantifying when and where such differences occur provides insight into which of these drivers is most likely. Here we examine song variation, (a) between sexes and (b) among the three geographically isolated subspecies, of the New Zealand Fantail (Rhipidura fuliginosa), a monomorphic passerine native to New Zealand. We measured twelve temporal and frequency parameters from recorded songs based on buzz notes. Only maximum frequency in one of the three phrases showed a significant sex difference, although there were suggestions of other sex differences in some element-level parameters. Song characteristics differed notably among subspecies; North Island Fantails typically produced shorter songs, comprised shorter elements at higher frequencies and faster element rates, while the most isolated birds (Chatham Island population), sang longer, slower songs. South Island birds were intermediate and more variable. The similarity of male and female songs suggests song is used by both sexes for similar purposes, while selection pressures associated with different habitats or cultural drift may be responsible for the song differences observed among sub-species. Further research analysing vocalisations of both sexes across a broader geographical range is required to further our understanding of female song function and patterns of geographic variation.