Demographic and Environmental Drivers of Canada Jay Population Dynamics in Algonquin Provincial Park, ON
Knowledge of the demographic and environmental drivers of population growth throughout the annual cycle is essential to understand ongoing population change and forecast future population trends. Resident species have developed a suite of behavioural and physiological adaptations that allow them to persist in seasonal environments. Food-caching is one widespread behavioural mechanism that involves the deferred consumption of a food item and special handling to conserve it for future use. However, once a food item is stored, it can be exposed to environmental conditions that can either degrade or preserve its quality. In this thesis, I combine a novel framework that identifies relevant environmental conditions that could cause cached food to degrade over time with detailed long-term demographic data collected for a food-caching passerine, the Canada jay (Perisoreus canadensis), in Algonquin Provincial Park, ON. In my first chapter, I develop a framework proposing that the degree of a caching species’ susceptibility to climate change depends primarily on the duration of storage and the perishability of food stored. I then summarize information from the field of food science to identify relevant climatic variables that could cause cached food to degrade. In my second chapter, I used 40 years of Canada jay reproductive performance data to understand how environmental conditions during the food storage period can carry over to influence brood size, nest success and nestling condition. I found evidence that fall freeze-thaw events, and, to a lesser degree, winter temperatures negatively influence all metrics of reproductive performance. In my third chapter, I investigated the effect of density and environmental conditions throughout the annual cycle on population growth. Fecundity was the primary vital rate driving variation in population growth and fall conditions had a strong indirect effect, acting primarily through fecundity, on population growth. In my fourth chapter, I investigated the mechanisms promoting density-dependent fecundity. I found evidence that site-dependent regulation is acting on fecundity, but only when environmental conditions are otherwise poor for breeding. Together my thesis highlights the importance of understanding how events throughout the annual cycle are connected and how such connections can, in turn, contribute to predicting population dynamics.