Bird migration through Minnesota tonight and Tuesday nights (Sept. 14, 15) is predicted to be substantial by BirdCast, an email alert service from the Cornell Lab of Ornithology.

The information comes from the web site Data is gathered by weather radar readings.

The prediction for Monday and Tuesday nights suggests migration numbers across the U.S. could reach 500 million birds.

The map below illustrates the prediction, white indicating high intensity movement.

Dr. Kyle Horton, assistant professor in fish, wildlife, and conservation biology at Colorado State University, guides collection of data. Asked to explain how this works he wrote, "Our model forecasts a radar-based value known as reflectivity. We are able to translate that into a number of birds by assuming the reflectivity is composed of uniform-sized birds.

"In this case, we assume the migrants are songbird-sized. Once we have an estimate of birds within spatial pixels, we sum up the number of birds moving over the U.S., states, and major cities.

"The numbers are predictions of migrants aloft three hours after local sunset in a height column from 50 meters to 2950 meters above ground level. Three hours after sunset is approximately the timing of peak migratory activity (i.e., it should represent the maximum number of birds aloft at any one time throughout the night).

For more information see