It's difficult to track birds flying across the sky in the dark of night, but every fall and spring, millions of birds migrate through the night. Weather radar can offer a spotty view of the phenomenon, but to track nighttime migrations with greater accuracy and reliability, a group of researchers at the University of Massachusetts at Amherst turned to artificial intelligence. Scientists designed a machine-learning algorithm to analyze weather radar images and differentiate migrating birds from precipitation. The algorithm replicates the power of neural networks to analyze and classify radar images. Researchers used the new artificial intelligence program to survey decades-long radar data sets, revealing seasonal and continent-wide migration patterns.