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Weather radar stations across the continental United States may predict “April showers” for some—but for the first time, new maps are using radar to forecast night-time clouds of migratory birds, plus track flights in near real-time.

Scientists with the Cornell Lab of Ornithology and the University of Oxford made the breakthrough—processing weather radar data to produce maps that visualize migration on the Cornell Lab’s BirdCast website (birdcast.info).

Migration Maps in Real-time

One map shows an animated visualization that tracks migration in near real-time (image below).

(Notice the intense migration wave starting right after sunset in Missouri, and how it slowly makes it way up into Iowa over the course of the night. These birds are covering about 400 miles in one night. The moving red line follows the time of sunset, east to west. The yellow line tracks sunrise. Arrows indicate the direction in which birds are flying. Adriaan Dokter, 2018.)

Cornell Lab postdoctoral associate Adriaan Dokter designed an algorithm to rapidly estimate the intensity and flight directions of migrating birds detected by the weather radar network.

The system processes incoming radar data continuously and updates the animated map every 10 minutes.

“We’re able to isolate bird data from atmospheric information because of the way weather radar works—a process called dual-polarization,” Dokter explains.

“This means the radar stations transmit and receive radio waves in both vertical and horizontal directions. It provides a much clearer picture of the size, shape, and direction of the targets it picks up. And with the power of cloud computing, we can analyze all radar data incredibly fast.”

Another map forecasts migration three days ahead. The color-coded displays combine projected weather conditions and bird movements to show where and when the most intense migrations are expected (map below).

This migration forecast map for the night of May 7, 2017, predicted high-intensity migration over much of the central U.S. “Hot” colors indicates more intense migration. Van Doren and Horton 2018.

Safe Migration of Songbirds

Most songbirds migrate in darkness, usually when weather conditions are favorable. Tailwinds can produce massive migratory movements. Rain can shut down flights entirely.

“Knowing when and where a large pulse of migrants will pass through is useful for conservation purposes,” says Benjamin Van Doren, a former Cornell undergraduate and now a Ph.D. candidate at the University of Oxford.

“Our forecasts could prompt temporary shutdowns of wind turbines or large sources of light pollution along the migration route. Both actions could significantly reduce bird mortality.”

“This is the most significant update since we first began using radar to study bird movements,” notes Cornell Lab postdoctoral associate, Kyle Horton.

“From the bird watcher’s perspective, if you know where and when migrants will be flying at night, you stand a better chance of seeing them, especially if the birds make a stopover in your area.”

Chipping Sparrows migrate by night, and their flight calls are a characteristic sound of the night sky in spring and fall in the United States.

Savannah Sparrows migrates mostly at night generally early in spring and late in fall.

Forecasting Migration Helps Conservation Efforts

Van Doren and Horton designed the system that generates the migration forecast maps. They used machine learning models based on 23 years of radar and weather data to predict suitable conditions for migration occurring three hours after local sunset.

“These forecast and live migration maps, and the research that produced them represent a breakthrough nearly 20 years in the making,” adds Cornell Lab migration researcher Andrew Farnsworth.

“We hope these maps will provide perspective to the expert and novice alike on the amazing spectacle—and the sheer magnitude—of migration. Beyond that, we believe these maps will become powerful tools for conservation action to help reduce the impacts of human-made hazards birds face during their incredible journeys.”

This research was supported by funding from the National Science Foundation, Leon Levy Foundation, and NASA. Additional funding was provided by the Edward W. Rose Postdoctoral Fellowship at the Cornell Lab of Ornithology, Marshall Aid Commemoration Commission in the United Kingdom, and Amazon Web Services Cloud Credits for Research.

The BirdCast project is a collaboration among the Cornell Lab of Ornithology, University of Massachusetts Amherst, and Oregon State University, and was funded by grants from the National Science Foundation and Leon Levy Foundation.