Measuring the effects of supplementary feeding and biosecurity on the trajectory of a threatened avian population

When faced with emerging infectious diseases in wild populations, conservationists are often forced to respond rapidly, with decisions based in uncertainty. Clear decision-making processes are rarely followed and subsequent monitoring and evaluation as to the efficacy of the chosen solution is often neglected. This thesis interrogates the interaction between disease transmission and population management solutions for the recovery of the endangered Mauritius parakeet (Psittacula eques), with a particular focus on nest sites, supplementary feeding hoppers and biosecurity. Beak and feather disease virus (BFDV; Circoviridae), the etiological agent of Psittacine beak and feather disease (PBFD), is widely infectious and fatal. PBFD is considered the most common viral disease in wild parrots and was first detected in Mauritius parakeets in 2005. Here I apply a combination of field-based experiments and molecular genetic techniques to screen both host and environmental DNA for BFDV, alongside observational, demographic and breeding data to address three key research questions. I assess the influence of (i) the wildlife trade in the global spread of BFDV, (ii) artificial nest sites and supplementary feeding hoppers on the prevalence of BFDV in Mauritius parakeets, and (iii) sociality at supplementary feeding hoppers on the transmission of BFDV. The key aim of this thesis is to provide practical and implementable management solutions that are relevant to any conservationists managing wild populations affected by BFDV.

I detected BFDV in wild parrots from eight new countries, as well as from birds seized from illegal trafficking. Phylogenetic associations between geographically distant regions highlight the impacts of the wildlife trade in the spread of infectious disease globally. With regards to population management, I found that there is currently no observable relationship between nest site placement and either BFDV prevalence or fecundity, but the relationship between BFDV prevalence and nest altitude may be of greater relevance under future climate change scenarios. Whilst biosecurity protocols applied at nest sites successfully reduced BFDV prevalence in nestlings, upscaled disinfection of hoppers had no significant effect. However, both forms of biosecurity unintentionally and significantly hindered Mauritius parakeet breeding success. Finally, I determined that the relationship between BFDV prevalence and hoppers was better attributed to the artificially altered frequency of social interaction between individuals at these centralised hubs.

These results have both increased our knowledge of BFDV occurrence globally, covering some highly biodiverse but data deficient regions, and provided an evidence-based approach to the evaluation of in situ pathogen management. Management for wildlife conservation should be critically evaluated through targeted monitoring and experimental manipulation, and this evaluation should always focus on the fundamental objective of conservation.