Testing the function of petal-carrying in the Red-backed Fairy-wren (Malurus melanocephalus)

In most species of fairy-wren (Malurus spp.), males are known to carry brightly coloured petals and display them to conspecifics. Although petal-carrying by males is often considered an inter-sexual courtship display, anecdotal observations suggest that it may also serve an intra-sexual aggressive function. In this study, we tested hypotheses for the function of petal-carrying displays in the Red-backed Fairy-wren ( Malurus melanocephalus) through behavioural observations and aviary-based experiments. All petal displays observed were perpetrated by males, with 90% directed toward females and 10% toward other males. Most petal displays were performed by males in nuptial plumage during intrusions into neighbouring territories, and most displays coincided with the potential fertile period of the female to whom the display was directed. Display items consisted primarily of seeds from Gahnia sp. and flowers from Banksia sp. and Lantana sp., all of which were red or pink and similar to the red backs of nuptial males. Aviary trials found no significant difference in the responses by adult females or adult males to stimulus males with or without petals, substantiating neither a courtship role nor an aggressive role for the display. On the basis of the context of displays in the field, we conclude that the petal-carrying display in the Red-backed Fairy-wren primarily serves an inter-sexual, courtship function, though we could not rule out an intrasexual, aggressive function.