Biology subjects

Cameron, T. C.

Publications and source records attributed to Cameron, T. C..

3 recordsLinked to original sources

bioRxiv2026

Exploring sources of uncertainty in the estimate of waterfowl harvest in the United Kingdom

There is an urgent need to gather data on harvest rates of waterbirds in Europe to assess the sustainability of hunting. Estimates of total waterbird harvest in the United Kingdom (UK) and the relative harvest of different huntable species come from two separate surveys, the Value of Shooting (PACEC 2014) and National Gamebag Census (NGC, Aebischer 2019), and these have been recently used to explore the likelihood of unsustainable harvests of wild waterbirds by UK hunters (Ellis and Cameron 2022; Madden et al., 2025). The reliability of these sustainability estimates depends on how representative the original surveys are of hunter behaviour and success. There are also 1-3 million released game-farm mallard (Anas platyrhynchos) that takes up considerable and unquantified proportions of the UK waterbird harvest. Here we explore uncertainties in the UK winter harvest of wild waterfowl by comparing estimates from the NGC dataset with those from the Crown Estate coastal hunting clubs, and a novel approach using analysis of social-media images (2019/20 to 2023/24). We explore the difference in species-specific harvest with and without the uncertainties in the number of released mallard and the total number of duck harvested in the UK. Waterbird harvest estimates differ markedly depending on the input dataset and whether released mallard are included in the analysis. Confidence intervals of each estimate are inflated by uncertainties in the number of released game-farm mallard contributing to, and the size of that national bag. Estimates extrapolated from social media suggest the national harvest of several species may be considerably larger than the corresponding NGC estimates (e.g. Teal *2.07 and gadwall *11.2), while mallard harvests away from formal shoots represented by NGC are significantly lower (*0.71). Excluding released mallard reduces the statistical estimate of total wild duck harvest by 56-63%, which would have biologically significant effects if realised.

ecology↗

bioRxiv2025

Fighting Through the Heat: How Sexual Selection Influences Demography Under Recurrent Heatwaves

Sexual selection is a potent evolutionary force with complex effects. Strong sexual selection can enhance adaptation and reduce mutational load, while simultaneously reducing survival, or causing sexual conflict that reduces fitness for one or both sexes. Many populations today face not only gradual environmental changes but also extreme, short-term stress events like droughts or heatwaves. The combined effects of sexual and environmental selection on population demography during and after such events remain poorly understood, even though such combined effects could be crucial for the persistence of small, endangered populations under climate change. In this study, we investigated how sexual selection affects survival during environmental stress by manipulating the expression of an aggressive fighter morph in small populations of the male-dimorphic soil mite Sancassania berlesei, exposing some of these populations to recurrent periods of extreme heat and monitoring survival over eight generations. We found that heat exposure reduced survival, more severely in females than in males, and survival was lower in populations with higher fighter prevalence, but there was no interaction between temperature and fighter morph prevalence. Furthermore, survival declined across generations, and the decline was steeper in populations with lower prevalence of fighters, leading to the loss of their initial survival advantage by the last generation. T265625hree populations exposed to heat became extinct during the experiment, all from the reduced fighter expression treatment. Our findings imply that despite its cost to individual survival, sexual selection does not modulate population sensitivity to heatwaves over several generations. Furthermore, we demonstrate that these mortality costs of sexual selection are gradually compensated over successive generations, which could be a result of a more effective purging of inbreeding depression. Thus, while the additive effect of sexual selection and heatwaves on survival may increase demographic risks for bottlenecked populations in the short term, sexual selection may increase resilience of populations to prolonged bottlenecks.

evolutionary biology↗

bioRxiv2022

An initial assessment of the sustainability of waterbird harvest in the United Kingdom

O_LIThere is a need to assess the sustainability of wild bird harvest in the United Kingdom (UK), and more widely, across Europe. Yet data on populations and harvest sizes are limited. C_LIO_LIWe used a Demographic Invariant Method (DIM) to estimate Potential Excess Growth (PEG) for populations of UK wintering waterbirds and calculated a Sustainable Harvest Index (SHI) for each. We compared this with population trends and conservation classifications (e.g. Birds of Conservation Concern; BoCC) to assess the sustainability of harvests and the utility of these classifications. C_LIO_LIOur approach found evidence for potential overharvest of mallard Anas platyrhynchos, Eurasian teal Anas crecca, gadwall Mareca strepera, Canada geese Branta canadensis, greylag geese Anser anser and woodcock Scolopax rusticola. Whether DIM methods predict overharvest is highly dependent on estimates of maximum population growth rates inferring PEG. We found estimates of maximum population growth to be variable across a range of different methods. C_LIO_LIWe found no relationship between SHI and short-term wintering trends or conservation classification under the UKs BoCC framework. There was however a positive relationship between SHI and long-term wintering trends. Policy Implications: Our results suggest that UK based harvest is unlikely to be a major determinant of population trends for the majority of UK overwintering waterbirds, but harvest rates for some species may exceed that required to maintain stationary population growth. The lack of a relationship between conservation classifications and SHI strongly suggests that such conservation classifications are not an appropriate tool for making decisions about harvest management. Instead, our assessment provides the basis for a framework to make evidence-based decisions on sustainable harvest levels in the face of incomplete data. There is currently no clear policy instrument in the UK to support such a framework via controls on either harvest effort or mortality of waterfowl. C_LI

ecology↗