Speaker: Courtenay Strong, Professor of Atmospheric Sciences, University of Utah
The facultative migration of avian species like Pine Siskins is primarily influenced by climate variability, which disrupts food availability and triggers irruptions—unpredictable, large-scale migrations caused by sudden resource shortages. This study investigates how atmospheric patterns contribute to climate-driven anomalies in seed production, which in turn drive these irruptions. In terms of mechanisms, the primary drivers of irruptions are often remote tropical storminess that triggers ocean-crossing atmospheric waves. Regarding timing, climate variability offers a surprisingly straightforward explanation for why certain irruption patterns occur sporadically, roughly once per decade.