Collaborative Proposal: RAPID: How do extreme flooding events impact migratory species?

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Extreme weather events can alter resources in dramatic ways, which can have positive, negative, or neutral impacts on species. In the case of hurricanes and tropical storms, heavy rains could trigger an unusual pulse of plant growth or, if extreme, drown critical resources. This substantial shift in resource availability almost certainly impacts the survival, reproduction, and growth of local populations; however, the extent to which migratory species are impacted is much less clear. Out-of-season resources may disrupt migration as individuals alter their normal behaviors, with potential negative consequences if arrival to winter or summer habitat is delayed or blocked. Alternatively, migratory species may avoid gaps in resources by shifting their routes, or even capitalize on resources that peak following heavy rainfall events, improving their survival at stopover locations and fitness at destination habitats. Texas is a critical migratory pathway in North America for many species of birds, bats, and insects and its position bordering the gulf coast means that it is also subject to many severe weather events during the tropical storm season. The recent flooding associated with Hurricane Harvey, the most extreme rainfall event in US history, provides a unique opportunity to investigate how plant resources shift in response to disruptive weather events. Further, hypotheses on the demographic responses of migratory species will be rigorously tested at both local and regional scales. This project will study the impact of Hurricane Harvey on a model migratory species, the eastern North American monarch butterfly (Danaus plexippus L.) population, with the goal of developing a framework to understand the impact of extreme flooding events on migratory species. The results will inform conservation efforts for the monarch butterfly, population models, and climate forecasting. This research will examine the effects of Harvey on monarch dynamics in the local Texas migratory corridor and evaluate the potential for carry-over effects into the monarch's overwintering population in Mexico and summer breeding population in central and eastern North America. The project will accomplish this through three key activities. First, data will be collected at survey sites throughout the affected area during the fall, winter, and spring of the 2017-2018 migratory season. Second, the impact of Harvey and other recent extreme rainfall events will be explored using climate data and remotely-sensed satellite imagery to model vegetation growth. Finally, monarch population models will link local conditions in Texas to the overwintering population in Mexico, and subsequently to spring and summer generations. This research advances macrosystems ecology by expanding the spatiotemporal scale at which carry-over effects from resource disruptions may impact migratory species, and providing a framework for incorporating conditions experienced by animals during migratory periods (the least-studied stages of the annual cycle) into population models to evaluate mechanisms governing long-term trends.