Mitigating costs of increased workload during reproduction
It has long been assumed that many activities of free-living animals are energetically demanding or “hard work”, for example, avian migration. If animals are working hard, especially during reproduction, it is likely they might pay a cost of increased workload: a “cost of reproduction” - that is, the idea that individuals can maximize lifetime reproductive success only by increasing workload to allocate resources to current offspring against the production of future offspring and self-maintenance. Nonetheless, over the past 50 years, studies of the trade-off between parental effort and survival have provided equivocal evidence, especially in female birds, with many failing to find any support while others find evidence against it. Therefore, if parental care is so costly, why is it so difficult to demonstrate negative (e.g., physiological) effects of the intense activity associated with chick-rearing? In an experimental approach using weighted backpacks to artificially increase workload, tri-axial accelerometers and GPS units to track daily movement and daily energy expenditure, and an automated nest box weighing system to collect fine-scale mass data, the goal of my PhD research is to investigate several physiological and behavioral mechanisms birds may employ to attenuate the costs increased workload associated with reproduction. For additional information on this work, check out Brett’s personal webpage. |
Intraclutch variation of egg size in insects
Individual quality (variable and correlated with fitness) is determined by phenotypic (e.g., body size) or life-history traits (eg. fecundity). Although many studies have focused on phenology and fecundity, few studies have researched the causes and consequences of intraspecific variation of egg size. Fewer studies have considered the impact of warming temperatures due to climate change on ectotherms and their future fecundity. My research explores individual quality in Harmonia axyridis, the Asian ladybird beetle, a globally introduced predatory generalist, without post-hatching care. This project will include a literature review of egg size across insect taxa and a lab component to manipulate individual quality under increase temperature. Our findings for individual egg size variability will provide base knowledge that can project population trends under warming temperatures. Further, it will contribute to a better understanding of the trade-offs and the mechanisms behind egg size variation within a species. |
Individual variation, plasticity, and co-variation of egg size in the European starling
Avian egg mass varies markedly within populations, with the largest eggs measuring up to twice the size of the smallest, and ~70% of this variation is due to variation among individual females (Christians 2002). Many studies highlight the high repeatability of egg size, suggesting that this trait is relatively inflexible within individual female birds. In contrast, some studies continue to suggest that there can be substantial, “adaptive” plasticity in egg investment. If egg size is a phenotypically plastic life-history trait, we predict that it would show potentially adaptive variation in different ecological contexts (e.g. seasonally, yearly). Using data from a long-term study of European starlings (Sturnus vulgaris, 2002-2022), my research will a) analyse individual variation in egg size, focusing on phenotypic plasticity and b) analyse covariation between egg size, life-history traits, lifetime productivity, and survival. By understanding how egg size correlates with fitness and individual quality, this trait can be included in the suite of traits used to predict reproductive success. |
Anthropogenic impacts on a seabird in the Salish Sea ecosystem
Seabirds are useful biomonitors of marine environments, which are increasingly impacted by anthropogenic activity. This is especially true in the Salish Sea, Pacific Northwest, but this area remains highly biologically productive providing year-round habitat for marine top-predators, including Glaucous-winged gulls (GWGU; Larus glaucescens). In recent decades, GWGU populations have declined in the Salish Sea concurrent with a dietary shift to more terrestrial prey. In collaboration with Environment and Climate Change Canada, we are investigating the wintering habitat use and contaminant exposure of GWGU throughout the Salish Sea. By evaluating the relationships between diet, contaminant burdens, and physiological health of GWGUs, as well as habitat use determined using GPS tags, we aim to better understand the impacts of anthropogenic activities on the health of GWGUs and the Salish Sea Ecosystem more generally. |