Supplementary feeding, life history and population dynamics : quantitative assessment of conservation strategies for red-billed choughs

• Main Author: Fenn, Sarah R
• Format: Dissertation
• Language: English
• Published: University of Aberdeen 2022
• Subjects: Birds; Red-billed chough

Evidence-based design, assessment and refinement of targeted management interventions for threatened populations are key pillars of effective conservation science. However, evaluations of interventions are often incomplete, impeding conservation success. For example, evaluations rarely quantify variation in impacts among target individuals or across time, collateral impacts on non-target conspecific individuals or life-history traits, or associated implications for overall population outcomes. Yet, explicit quantification of such impacts would not only inform effective and responsive management practices, but may also highlight complex ecological constraints on population growth rate (λ), thereby advancing wider conceptual knowledge and reinforcing feedbacks between pure and applied ecological research, to the benefit of both. In this study, I quantify the demographic and population impacts of a targeted, multiyear supplementary feeding intervention on the threatened Scottish red-billed chough (Pyrrhocorax pyrrhocorax) population, designed to ameliorate threats to viability posed by critically low, food-limited first-year survival. I first estimate intervention impacts on target juvenile survival, finding both within-year and among year variation in management efficacy. Substantial positive management impacts on juvenile survival ultimately reduced, but did not prevent, further population decline. Second, I identified substantial positive collateral intervention impacts on adult vital rates and resulting λ, which were themselves near sufficient to achieve short-term population stability, regardless of impacts on target juvenile survival. Finally, I utilise the long-term dataset to quantify dynamic patterns of dispersal, and then quantify implications of observed patterns of opposing sex-specific, density-dependent natal dispersal distance for population kin structure. Overall, this study contributes towards the ambitions of evidence-based conservation, providing comprehensive quantitative evaluation of a targeted intervention to inform conservation policy, and highlight opportunities for refinement. Furthermore, I discuss how several key results are of wider interest for both conservation science and practice, as well as for fundamental understanding of population processes.