As a group, birds are facing continued declines in conservation status. As such, ex situ management is becoming a more widely used and important tool in conservation programmes. However, adaptation to captivity and behavioural change during ex situ breeding programmes may reduce the success of these interventions. Changes in mating traits, such as vocal behaviour, may be particularly important. In this thesis, I examine the potential for vocal evolution during ex situ conservation to determine how it could impact conservation efforts, focusing on the Java sparrow (Lonchura oryzivora), an endangered estrildid finch. Firstly, I examine the existing literature to determine how vocal behaviour could impact on conservation actions and how potential problems could be mitigated (Chapter 2). Vocal learning and the formation of population dialects have particular significance in conservation programmes due to their effects on important behaviours, such as mate choice. Java sparrows learn a number of components of their song, including song complexity and note acoustic structure (Chapter 3). Birds also learned many temporal features of song, such as tempo, the inheritance of which has been less frequently studied (Chapter 4). Given the importance of vocal learning in song development, there is a high potential for vocal change and population divergence during ex situ breeding in this species. Such differences are important for mate preference; Java sparrow females preferred familiar, over unfamiliar, songs (Chapter 5). Preference for familiar songs may result in assortative mating between individuals of different population origin during conservation efforts, reducing the effectiveness of conservation programmes. As well as behavioural changes, other phenotypic changes may occur in captivity. Captive Java sparrows were both larger and had greater sexual size dimorphism than those of wild origin (Chapter 6). Morphological changes during captive breeding may reduce the performance of captive-bred individuals in wild environments, as well as affecting other, correlated traits, such as vocal behaviour. Vocal behaviour may also be affected by altered sound environments experienced by birds during ex situ breeding programmes. Human presence has a significant effect on the zoo soundscape; reduction in human presence during the COVID-19 lockdown was associated with a number of changes in the sound environment (Chapter 7). Overall, there is significant potential for vocal evolution during the captive breeding of Java sparrows, mediated by cultural processes resulting from social learning of vocalizations, environmental differences, and other, correlated changes. Changes in vocal behaviour in the Java sparrow could affect conservation programmes due to preferences for familiar vocalizations in this species by contributing to assortative mating. The findings from this species suggest that vocal behaviour can have an important role in the success of conservation efforts and requires further investigation in this and other species.
|Date of Award||1 Aug 2023|
- The University of Manchester
|Supervisor||Susanne Shultz (Supervisor) & Robert Gilman (Supervisor)|