Conserving woodland birds : the need for population data in evidence-based planning

Abstract

Arresting biodiversity loss is integral to protecting the intrinsic value of natural areas and the ecological services that are critical for human well-being. The important role that birds play in supporting a suite of ecosystem functions underpins the need to identify processes that drive long-term change in populations of this group. Indices of population change are frequently used to communicate important trend patterns for species. However, for such indices to assist the objectives of biological conservation and human development, a deeper understanding of the processes that drive population change is essential. Consequently, identifying factors that stress and pulse species populations has become a dominant theme in global conservation research. Currently, there is concern for the persistence of birds throughout the temperate woodland regions of Australia. Native vegetation in these regions has been extensively cleared and modified since European settlement in the 1800's. Furthermore, ongoing threats to woodland extent and condition prevail, such as agricultural and urban expansion. In this thesis, I analyse an exemplary, volunteer-collected dataset to provide a detailed assessment of temperate woodland bird population trends over time, and the dominant factors influencing their persistence, in an important woodland region of Australia. My research shows that quantitative evidence for the decline of temperate woodland birds is limited, and that rigorous empirical research into the factors influencing woodland bird populations is needed to inform evidence-based conservation planning. I identify significant temporal dependence in the response of woodland bird species, and functional trait groups, to three key regulatory factors: weather, reservation and urbanisation. My assessment and analysis of these factors incorporates 14 years of empirical field monitoring data, revealing important biological responses that would not be detected in short-term research. Specifically, I demonstrate that the temporal scale, and conditions experienced during the period of trend assessment, will exert a significant influence on the calculation of population indices and, in turn, the conservation implications inferred. I show that woodland bird species are resilient to severe drought. I reveal that the impact of protected areas and urban development on woodland birds are interactive, and can change through time. I provide empirical evidence that ecologically-informed reserve selection achieves better conservation outcomes for species, and that a previously untested metric of urban encroachment (rate of urban change) exerts a significant influence over species distributions in time and space. These findings represent scientific evidence that can inform the planning of reserves, restoration activities, and ecological-sensitive urban design for birds occupying temperate woodland habitats. For this reason, I provide a synthesis of management implications and recommendations to enhance decision making for this threatened assemblage of species in Australia. In addition, the results presented in this thesis make an important contribution to the conservation science of managing declining populations. In particular, I present a novel tool for the evaluation of methods used in population trend assessment, as a means to improve future monitoring programs. In completing this work, I highlight the extraordinary contribution that citizen scientists can make, and have made, to conservation research.