Explaining geographic variation in the elaborate vocal display of the male Albert's lyrebird Menura alberti

Abstract

In this thesis I investigate geographic variation in the song of the Albert's lyrebird (Menura alberti). The Albert's lyrebird is a large, Near Threatened, oscine passerine found in a restricted area of subtropical eastern Australia. Male lyrebirds are known for their extended bouts of vocal mimicry that form part of an elaborate multimodal display, but males also produce their own, species-specific vocalisations. Albert's lyrebirds have experienced substantial habitat loss since European settlement, and are highly sedentary, restricting cultural transmission between geographically distant populations and allowing for considerable variation in vocalisations across the range. Geographic variation in both species-specific song and mimetic song has been anecdotally reported, but never formally quantified. The Albert's lyrebird's complex, variable vocalisations make it an ideal model species to investigate geographic variation in a range of vocalisations (described in Chapter 2). Furthermore, as Albert's lyrebirds are a threatened species, it is important to document existing behavioural variation. Such variation may then be used to identify potential targets for conservation. Overall, I found that male Albert's lyrebirds exhibit significant geographic variation in multiple vocalisation types and at several levels of song organisation. These patterns of geographic variation highlight the complexity of geographic variation in vocalisations. I also demonstrate how geographic variation can provide insights into other aspects of vocal behaviours. Through variation in mimetic repertoire size, composition, and organisation, I provide evidence that mimicry is at least partially learnt from conspecifics, in line with previous research suggesting that mimicry is learnt from both conspecifics and heterospecifics. The high acoustic contrast between consecutive units within the sequences of all populations suggests that repertoire complexity is an important feature of the vocal mimicry. I highlight the need to investigate temporal organisation of mimetic repertoires in other mimicking species in order to understand the function of mimicry across multiple taxa. Finally, I demonstrate the impact of anthropogenic habitat change on the cultural diversity of Albert's lyrebirds, and suggest that mimetic diversity may provide an indicator of population health. This thesis adds to the growing body of literature on the impacts of anthropogenic disturbance on vocal diversity, and how vocal cultures may be useful in conservation management.

Date of Award	2021
Original language	English