Regulation and risk: developing models to assess the dynamism of seabird populations and their risk from anthropogenic mortality

Miller, Julie A. O. (2020) Regulation and risk: developing models to assess the dynamism of seabird populations and their risk from anthropogenic mortality. PhD thesis, University of Glasgow.

Abstract

In the face of expanding industry, the assessments undertaken to preserve biodiversity from damaging impacts from anthropogenic development require robust approaches that capture population processes, associated uncertainties and predict outcome scenarios with increased precision. The offshore wind industry has the potential to negatively impact upon UK seabird populations via additional mortality, but arguably has many benefits towards globally reduced carbon output. Here, I examine current practice in impact assessment of seabirds and by use of state-space integrated modelling approaches provide methods of estimating demographic processes in models fitted to commonly available empirical data. By provision of these estimates I then simulate outcomes of additional anthropogenic mortality to real populations.

In this way, in chapter two I find intrinsic (density-dependence) and extrinsic (environmental stochasticity) regulation operates differently in sympatric species, affecting population persistence under thresholds of regulation and exacerbated by additional mortality. I find consideration of basic connectivity (a rescue-effect) confers some reduction in the magnitude of impacts observed.

By investigation of the regulation of a vulnerable, declining species, I show in chapter three evidence of age-specific regulation, potentially a result of a trade-off between experience and breeding costs. I highlight important covariates of regulation for productivity and the difficulty in identifying drivers in survival.

The exclusion of connectivity of seabird populations is an important omission in population assessment. In chapter four I identify a region of potential connectivity and in a hierarchical state-space model, fitted to incomplete time-series of two demographic indicators (productivity and adult nests), estimate transfer probability between 84 sub-populations of a species on the Shetland archipelago. In subsequent stochastic simulations, I apply mock additional mortality to the region under various treatments, finding different spatial patterns of decline and persistence, comparative to the traditional closed approach.

Together, these studies provide methods and evidence for increased ability to predict unknown outcomes across a range of potential scenarios with increased reality and representative uncertainty. The results capture the importance of consideration of the ecology of the species during parameterisation of models to represent important demographic regulation (the three sympatric species, differently responding to regulation). The results also make a case for further consideration of differential magnitude of effect of regulation to each vital rate and finally, in concordance with metapopulation theory the results highlight sub-population persistence dynamics vary comparative to closed population outlooks. These findings have immediate application to population modelling and provide a general method and framework for further investigations of both population dynamics and forecasting persistence.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > Q Science (General)
• Colleges/Schools: College of Medical Veterinary and Life Sciences > Institute of Biodiversity Animal Health and Comparative Medicine
• Supervisor's Name: Matthiopoulos, Prof. Jason
• Date of Award: 2020
• Depositing User: Ms Julie Miller
• Unique ID: glathesis:2020-81268
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 15 Apr 2020 13:40
• Last Modified: 12 Aug 2026 08:55
• Thesis DOI: 10.5525/gla.thesis.81268
• URI: https://theses.gla.ac.uk/id/eprint/81268