Sequential mountings of a possible immature male by an adult male in Victoria's Riflebird (Ptiloris victoriae)

Few studies have offered detailed descriptions of copulatory behaviours in the birds of paradise (family Paradisaeidae) and systematic investigations of their sexual behaviours are rare. We recorded courtship behaviours of Victoria's Riflebird Ptiloris victoriae in the Atherton Tablelands in Queensland, Australia using motion triggered cameras and report a rare case of three sequential mountings by an adult-plumaged male. While the recipient of these mountings performed female-typical sexual behaviours, it also briefly performed a male courtship display behaviour, suggesting that it may be an immature male. This observation raises several questions about the courtship behaviour of this species. Females may, for instance, occasionally solicit multiple copulations from preferred males to maximize the amount of transferred sperm. Another intriguing possibility is that immature males tolerate being mounted and potentially even mimic female sexual behaviours when learning from the displays of adult males. We also describe a novel adult male sexual behaviour, namely 'nape-pecking'.