Lunch & Learn Series: Autumn Raptor Migration Timing

For HMANA’s March 2024 Lunch & Learn series, we welcomed Boise State University graduate student, Nora Honkomp to talk about her research focused on raptor migration timing and climate change.

To assess and predict the effects of shifts in raptor migration timing because of climate change, we must first understand the mechanisms underlying the timing of this phenological event. The timing of raptor autumn migration is dependent on both biological and environmental factors, and different species rely on different cues for determining when to migrate. However, these specific factors among raptors have not been fully identified. We used eBird data to determine the autumn departure timing of 15 raptor species across North America over the last decade. Using this information, we compared the importance of several life history traits among the species for determining within-season departure timing and variability in departure timing across space and time. Latitude of breeding, migration distance, social behavior during migration, and body mass were important factors for determining seasonal departure timing, while social behavior, diet generalization, and migration distance were important for determining variability in departure timing. Also, we selected four raptor species to explore the impact of seasonal temperature, precipitation, and snow cover for determining departure timing.