Abstract
For a species to succeed, individuals must be able to attract a mate. The method in which they do this is known as a breeding system and it involves a diverse array of social behaviours. A lek breeding system is employed by some polygynous species and is characterised by aggregations of males that females visit primarily for breeding purposes. This results in strong sexual selection pressures on the lek, as males compete for females and females ‘choose’ between males. The kākāpō (Strigops habroptilus) is a critically endangered, nocturnal parrot, endemic to New Zealand. Kākāpō are also the only species of parrot with a lek breeding system but female kākāpō only breed every two to five years in response to the masting of rimu (Dacrydium cupressinum) trees. Male kākāpō acoustically and visually display on the lek and are subsequently visited by females. Acoustic displays are an effective method of communication, as components of this display can convey information to females about the quality of a male, thus informing her mate choice. However, little is known about the role that vocalisations play in female kākāpō mate choice or why some males are more successful than others. The first objective of this research was to characterise the three main vocalisations of kākāpō (booms, chings, and skraaks) and investigate their role in female mate choice by analysing the relationship between acoustic parameters and life history traits of male kākāpō using recordings of their vocalisations. Most parameters of vocalisations were not reliable indicators of identity, nor were parameters of vocalisations associated with male reproductive success. Duration and inter-boom/ching duration were the only parameters with sufficient individual variation to signal for identity, but individuals could not be discriminated between based on these two parameters. Vocalisations did not appear to function as honest indicators of age, weight, or origin based on the linear features analysed in this study. There were differences in the dialect of Fiordland kākāpō and Rakiura/Stewart Island and Whenua Hou/Codfish Island kākāpō, but not between those from Rakiura and Whenua Hou. There were temporal patterns between booming and chinging and vocalisations changed over the course of the breeding season. Non-linear phenomena were only present at low frequencies in chings and skraaks. Therefore, the role of male kākāpō vocalisations in female mate choice is still unclear. If vocalisations are not honest signals, females may be using different criteria to select a mate. However, if females are able to recognise males based on the duration and inter-boom/ching duration parameters, they could become attuned to their preferred male, explaining the prevalent skew in reproductive success. A skew in reproductive success is common on leks, which is known as the lek-skew paradox. There are several models, such as the hotspot and hotshot model, that seek to explain why males still gather on a lek despite little or no chance of breeding, which both conclude that males have a greater chance of breeding by gathering on a lek than they would have displaying alone, resolving the lek-skew paradox. Alternatively, males could indirectly benefit by gathering on a lek to increase the reproductive success of a relative (kin selection). However, kākāpō have low genetic diversity, and clustering with kin on a lek could further reduce this. The second objective of this thesis was to investigate the possibility of kin clustering on kākāpō leks using genetic relatedness coefficients. It appears that male kākāpō do not cluster with their kin, and instead, simply migrate to the lek closest to their winter home range whereas female kākāpō visit the largest lek. Both male and female kākāpō also exhibit strong site fidelity and male breeding activity is correlated with the mast level of rimu. Therefore, male kākāpō are not gaining indirect benefits by breeding on a lek and must be gaining direct benefits by exhibiting lekking behaviour, however, what these direct benefits may be is still unknown. When the models used to justify the lek-skew paradox are applied to kākāpō, one single model cannot completely explain this behaviour. It is more likely that a combination of factors are responsible for the maintenance of lekking behaviour in the kākāpō. This study highlights the importance of understanding breeding systems, as this information can have a critical role in the management and conservation of endangered species.