Photo 1 – When will the peak migration period reach your area this spring? (Chestnut-sided Warbler photo by Paul Konrad).
An exceptional map that provides peak migration dates as birds migrate north across the continental United States was produced by BirdCast researchers (graphic by Audrey Carlsen; BirdCast data analysis by Adriaan Dokter).
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The timing of spring migration varies across the United States and even within regions of the nation. To determine the peak periods of spring bird migration, BirdCast researchers have analyzed radar data collected over a 10 year period from 2013 to 2022. The peak period was defined as when the nightly average number of birds in the night sky was greatest, as measured by 143 radar systems positioned from coast to coast. During the study period, radar systems measured aerial bird densities every 10 minutes, providing some very detailed information down to the county level in each state.
Eager birders are now able to see when their peak bird migration should be happening, according to the BirdCast analysis. BirdCast has definitely become an important tool that birders use to learn more about birds and bird migration on a seasonal and even a daily level.
BirdCast is a collaboration among researchers at the Cornell Lab of Ornithology, Colorado State University, and University of Massachusetts Amherst that use weather radar and machine learning to track and even forecast bird migration. BirdCast senior researcher Adriaan Dokter, a research associate at the Cornell Lab, said differences in bird migration timing can be seen not just across the continent, but even within some regions. “One thing that stood out to me is how the western Gulf of Mexico and Texas have later peak migration dates than the eastern Gulf,” Dokter explained, noting that the difference is driven by the species composition of bird migration in those 2 areas.
“By far the most long-distance migrants [birds such as warblers and orioles that are migrating from wintering ranges in Central America and South America] arrive in the United States in the western Gulf States and through Mexico, and way fewer arrive in the East. The Southeast is the main region where lots of common short-distance migrants winter, and these birds migrate several weeks earlier.”
Dokter noted that the same pattern plays out in California’s Central Valley, where there is an island of overwintering areas for short-distance migratory birds surrounded by the flight paths of long-distance migratory birds. He also points out that a corridor from western Texas north to the Dakotas registers relatively earlier peak bird migration periods compared to surrounding areas. “It’s nice to highlight that the Great Plains is a main highway for migration, where birds enter the country, move north, and then distribute west and eastward,” he added.
Learn more about birds and bird migration by using BirdCast’s migration tools:
- Bird migration forecast maps
- Migration dashboard Explore nightly migration info and species migrating in your area.
To refer to the original article authored by Gustav Axelson and Pat Leonard that was published in the All About Birds website, refer to When Will Spring Bird Migration Hit Its Peak? BirdCast Has Answers | Living Bird | All About Birds