Climatic drivers of continental-scale bird migration in spring
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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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Abstract
Avian migration studies conventionally divide North America into three or four primary flyways.This strategy has been adopted for convenience or determined by the time-averaged movement patterns, so it may not adequately reflect the real temporal variability of bird migration phenology. Using a unique radar-based data set (NEXRAD) covering the contiguous U.S. (CONUS), and an objective regionalization approach, we have identified two regions with distinct interannual variability of spring migration. This two-region approach helped us to distinguish the climatic drivers of year-to-year variability specific to the western and eastern CONUS. For example, we identified an east-west dipole pattern in migratory behavior linked to atmospheric Rossby waves that appeared to be triggered by oceanic forcing in the tropical Pacific. Our results offer a new geographic framework that would facilitate exploring the climatic cues affecting the interannual variability of migration phenology at the continental scale.