Conservation and management of the forty-spotted pardalote (Pardalotus quadragintus)

Abstract

The human impact on natural environments is happening at an unprecedented rate. In addition to well-known threats that have created the current biodiversity crisis (deforestation and habitat degradation, biological invasions), climate change is now considered one of the main threats to biodiversity because is rapidly exposing organisms to new conditions and altering species interactions. These threats have led many species to require management intervention to survive. Despite conservation efforts, the number of species that have recovered after management remain small. Low success rate in species management can be attributed to severe lack of funding for conservation and 'evidence complacency' (i.e. use of anecdotes rather than evidence) by many conservation practitioners. However, lack of research to guide evidence-based actions, and uncertainty about how to manage existing threats can also be sources of failure. Understanding population dynamics and finding solutions to mitigate known threats can provide managers with critical information to guide decisions, increasing chances of success. For example, is habitat restoration the only action needed? Or is genetic management also necessary? Without investigating important populations parameters (e.g. abundance, genetic diversity, dispersal), it becomes hard to decide on the best interventions to be taken. This thesis focuses on filling research gaps on the endangered forty-spotted Pardalotus quadragintus to inform its management. Forty-spotted pardalotes are a small passerine endemic to Tasmanian forests, where their preferred food tree, white gum (Eucalyptus viminalis), occurs. They have become extinct across most of their former Tasmanian range due to deforestation and habitat degradation and are now mainly restricted to two offshore Islands (Bruny and Maria), and small forest patches on southeast Tasmania. The species is listed as endangered under the EPBC act and the IUCN red list and threats limiting remaining populations include ongoing habitat degradation, low nesting site availability, competitors, and parasitism. Given the current fragmented nature of populations, conservation translocation has been proposed for the species. However, there is little information on population dynamics and threats to decide whether embarking on an intensive and expensive form of management, such as translocation is the best option. This thesis focuses on filling these research gaps, and together with the introduction and conclusion, it comprises five data chapters. In chapters one and two, I used ecology and genetic data to investigate important population parameters and genetic health of remaining populations. In chapter three, I modelled the distribution of forty-spotted pardalotes' preferred food tree (white gums) across Tasmania, under current climate and future climate scenarios to identify areas on which to focus future on-ground habitat assessment with a view to selecting sites for translocation trials. Parasitism of nestlings by the larvae of an ectoparasitic fly Passeromyia longicornis has recently emerged as a new threat to pardalotes. In chapter four, I used data on the breeding biology of the forty-spotted pardalote and the common striated pardalote in a climate window analysis to investigate how winter temperatures (prior to the breeding season) mediate this host-parasite interaction. Finally, in chapter five I present a field experiment to test a low cost management technique to control parasites and boost nest productivity in the endangered forty-spotted pardalote. In the conclusion, I discuss the impact of multiple threats to forty-spotted pardalotes, and the potential revealed by my research for mitigating at least some of them. I outline the best ways to secure their future, including the further research needed and management interventions that can be applied to remaining populations and incorporated in reintroduction trials.