Of acoustics and avifauna: An integrative approach to avian ecology across the Southern Hemisphere
Ecological monitoring is taking on greater significance as we try to better understand and mitigate anthropogenic impacts on Earth’s ecosystems and species. This has led to the development of more effective avenues of ecological inference and means to inform them. These include birds and their ecology, which often represent wider ecological processes reliably. Birds are also relatively easily observable, and not just visually. Vocalising taxa, like birds, are suitable subjects for acoustic monitoring. This compatibility has drawn increased focus to interdisciplinarity and integrated approaches to ecological research.
In this thesis, I aimed to adopt an integrated approach to avian ecology in different ecosystems across the Southern Hemisphere, with an emphasis on (but not restricted to) acoustic monitoring. As an introductory study, I conducted a systematic review of bioacoustics literature from Africa, which, as a continent, is particularly well suited for acoustics-based biodiversity research. I reviewed 727 publications, dating back to 1953. My analyses revealed an overall exponential increase in bioacoustics research output, but notable underrepresentation of non-mammalian, non-terrestrial, conservation/human impact, and African-led studies. My results help illustrate the potential for expanding the field of bioacoustics on several levels across Africa.
Following this, I used multi-year data (2013-2018) from bird surveys in a flood-pulsed dryland wetland in southern Africa to assess the responses of seven functional groups of wetland-dependent bird to varying (remotely sensed) inundation levels and fire frequencies. I used generalised additive modelling to help predict these responses, in an attempt to relate hydrological fluctuations to ecological processes along the central channel system of Botswana’s Okavango Delta. My models robustly predicted trait-based responses of wetland-dependent birds in the delta’s interior and showcase an avenue for long-term ecological monitoring in dryland wetland systems, to support management and mitigation efforts.
Finally, I used data collected from passive acoustic monitoring (PAM) and camera trap surveys to investigate the determinants of functional, phylogenetic, and taxonomic structures of bird communities in urban forest patches across Wellington City in Aotearoa New Zealand. These determinants were broadly divided into (1) forest patch characteristics and (2) relative predator abundances. I identified older forest stands, distance to a sizable ecosanctuary, and cat, possum, and rat (Rattus spp.) abundances as key determinants of urban forest bird community structures. This study presents further evidence of how functional and phylogenetic community measures can be driven by different determinants compared to taxonomic metrics. I highlight the value of these findings in an urban conservation and ecological restoration context and evaluate the use of acoustically derived bird species richness appraisal tools in urban forest habitats.
My thesis demonstrates how an integrated approach to avian ecology can help track ecological integrity and inform conservation strategies in a rapidly changing world.