Piping call diversity in the crimson rosella species complex: evidence of individual signalling

Abstract

Birds communicate using a wide variety of signals, including auditory, visual, and olfactory signals. Avian vocalisations have various functions, ranging from mate attraction, mate choice, and territorial defence, to the recognition of kin, species, or individuals. In order to perform these functions, vocalisations must vary, and often provide honest indicators of individual condition or quality, or individual identity. This study aimed to test for variation in the piping call of the crimson rosella, Platycercus elegans, species complex, in order to determine the possible function of the piping call. I analysed 480 calls from 89 unmarked individuals representing three subspecies of the crimson rosella, and a hybrid population. Ten acoustic variables were tested (call duration, number of elements, element duration, inter-element silence duration, risetime, falltime, maximum frequency, minimum frequency, peak frequency, and frequency bandwidth). This study shows that crimson rosella piping calls have high levels of individual variation, especially in frequency variables. I propose that local populations may have consistent basic call structure (call duration, number of elements), but that individual rosellas within populations could use distinctive frequency combinations as individual signals. There was little evidence to show that crimson rosellas display subspecies or ontogenetic variation in their piping calls. The findings of this study could be further tested with the use of playback experiments, and the study of piping calls of marked birds.