BirdCast’s New Dashboard Highlights the Hottest States and Counties for Bird Migration

From the Autumn 2022 issue of Living Bird magazine. Subscribe now.

During last fall’s migration season, Georgia took the top prize for the most birds— with 900 million birds migrating to the Peach State from August 1 to November 15. But the busiest fall migration night reached neighboring Alabama, where 33 million birds flew into Baldwin County on the night of October 16—the highest nightly total for any county.

These bragging statistics come from the new online Migration Dashboard produced by BirdCast, a collaboration of scientists at the Cornell Lab of Ornithology, Colorado State University, and the University of Massachusetts Amherst that uses weather radar and machine learning to track and predict bird migration. BirdCast has been tracking nightly bird migration via radar across the USA since 2018, but last spring the program launched the Dashboard tool to provide real-time migration data at the county level.

“In recent years, we’ve been able to detect and predict the movements of migrating birds across vast continents,” said BirdCast senior researcher Andrew Farnsworth, a research associate at Cornell Lab. “That’s fascinating, but now you can also feel what’s going on in your own neck of the woods.”

The Migration Dashboard provides realtime analytics about bird migration at night, such as flight speed, direction, and height. In the fall of 2021, BirdCast indicated that southern states like Alabama and Georgia had the highest amounts of migrating birds, which made perfect sense to radar ornithologists like Farnsworth and Adriaan Dokter.

“There is always the possibility that the migration will concentrate in the eastern Gulf [of Mexico],” said Dokter, a research associate at Cornell Lab and member of the BirdCast team. The reasons, he said, lie in the basic needs of migrating birds: shelter, food, and favorable air.

In the fall as the birds migrate south from their breeding grounds, they seek large tracts of forest to shelter and refuel on their exhausting journey. Dokter noted that the Appalachian Mountains—which are essentially 1,500 miles of unbroken trees running from Canada to the Deep South—were particularly attractive for migrants. The mountains collect birds from all over the East, releasing them to the southernmost points of the range in Georgia and Alabama.

Large numbers of birds also migrate to Midwestern states such as Iowa and Missouri. When flying in a favorable tailwind (that is, wind blowing out of the north), migrating birds tend to fly eastward due to prevailing west-to-east winds across the continent. Again, the birds were pushed toward Georgia and Alabama.

This confluence of migratory bird rivers—where birds flying down the Appalachians meet birds flying up from the Midwest—makes the Southeast a hub for bird night air traffic. .

The maximum number of bird migration nights is dictated by the weather.

“Birds love to migrate with a good tailwind,” Dokter said. In fact, the three biggest bird migration nights in the fall of 2021—on Sept. 22, Oct. 3, and Oct. 16—were all the result of high pressure systems that brought cold weather and favorable tailwinds from the north. But Dokter theorizes that there is a difference in the makeup of the species during the three great migration nights.

“It’s likely that the first peak will be more distant migrants,” he said. “Later we saw birds staying in the US through the winter.” In other words, birds like warblers that migrate as far as Central and South America leave first, while sparrows and kinglets that have less ground to cover migrate later.

As for the fall of 2022, Dokter says the new BirdCast tool adds a new element to birding in the fall migration. “I’ll sit there with the Migration Dashboard, look around, and let the birds surprise me,” he says.