A primer for using weather surveillance radar to study bird migration

Summary

A 24-hour national mosaic animation of radar imagery featuring large numbers of birds taking flight. Circular blue and green features represent bird migration; precipitation appears as irregular bands. (Base reflectivity radar imagery from October 16th-17th, 2017, 12pm-12pm EST.) Doppler weather radar data—like those shown in the animation above and often featured in weather broadcasts—can tell us much more than how much rain will fall on your weekend cookout. Here at BirdCast, we turn weather radar data into information on the numbers and flight directions of birds aloft in order to expand the understanding of migratory bird movement. We have been hard at work serving you products, like the new migration forecast and live migration maps. After several years (and hundreds of posts) describing migration, species on the move, and unique migration events, we want you to have a better understanding of what happens at BirdCast. In this article, we’ll give you a brief overview and a behind-the-scenes look at the ways we apply radar data to study bird migration. Check out our FAQ for more in-depth explanations of our work. MORE THAN WEATHER Radar, an acronym for radio detection and ranging, was originally developed to detect enemy aircraft in World War II. As the decades have passed, it has become a valuable tool for studying all kinds of objects in the atmosphere. One of radar’s most common applications is the detection of meteorological events—especially thunderstorms, tornados, and hurricanes. But there are other applications. The same radars that meteorologists use to estimate rainfall rates are equally adept at detecting other objects in the atmosphere, like birds. From the earliest years of radar development, engineers and operators noticed dots on their screens that confused them. These targets did not correspond to any weather condition or aircraft and were dubbed “angels” in honor of their transient nature. And confusion about these targets arose for good reason: ...