Population dynamics and conservation of animals in seasonal environments

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From Arctic to tropical ecosystems, virtually all organisms experience some form of ‘seasonality’ that is characterized by resource fluctuations over the course of an annual cycle. Annual resource fluctuations typically result in relatively long periods in which animals are devoted only to acquiring resources to survive (i.e. the non-breeding period) interspersed with a shorter period(s) where to focus shifts to reproduction (i.e. the breeding period). This alternation between breeding and nonbreeding seasons can have important consequences for individual fitness and population dynamics but has posed a major barrier in our ability to decompose the drivers of population growth and identify which season is driving declines. The primary reason for this is because the vast majority of studies in the wild still focus on a single period of the annual cycle (usually breeding). Over the next 5 years, I propose to take a multi-tiered approach to address my long-term goal of understanding how resident and migratory populations respond to environmental change. My first two objectives focus on using long-term datasets (30+ yrs) to understand how events throughout the annual cycle contribute to annual variation in population growth rates. Objective (1) focuses on carry-over effects and climate change in a declining boreal resident bird, the gray jay (Perisoreus canadensis). Objective (2) focuses on how variation in density and climate in multiple seasons act to limit and regulate a migratory bird, the Savannah sparrow (Passerculus sandwichensis). My third objective (3) is to use our now well-established experimental lab system (seasonal populations of Drosophila melanogaster), in conjunction with data from wild populations, to examine whether there are season-specific signals in species population counts that can indicate if population declines are a result of what is occuring on the breeding or non-breeding grounds. My proposed work combines emerging concepts (seasonal interactions, full annual cycle models) with innovative mathematical models (IPM & SEM) and state-of-the-art field tracking methods (ICARUS, Motus) and is explicitly designed to test causal mechanisms underlying population declines caused by environmental change. By combining our novel laboratory system with predictive models from our wild systems and citizen science data, we also explore a new avenue of research that offers promise for identifying where conservation resources should be most effectively allocated. My research will not only lead to valuable insights into our focal organisms but also provide fundamental examples of how incorporating seasonality is critical for understanding the mechanisms driving population growth.