By Erik Stokstad Apr. 5, 2018 , 4:15 PM
Each spring, billions of birds fly vast distances to spend the summer in North America, most of them traveling at night. It's a trip fraught with peril: Many slam into wind turbines or brightly lit buildings. Now, a new forecasting system for bird migration could help put an end to millions of those deaths by warning wind farm operators and building managers of incoming migrations 3 days in advance.
Although hawks and other large species migrate during the day, most small birds migrate at night to avoid predators and enjoy better flying conditions. The daily legs of these migrations depend heavily on the weather. If conditions are too cold or rainy, migrants hang out in trees until the skies clear. And birds are more likely to continue their journeys when warm air signals an incoming, southerly tailwind. Since 2012, the Cornell Lab of Ornithology has made predictions about these migrations by using observer sightings and regional weather reports on its BirdCast website.
To scale up and automate these forecasts Benjamin Van Doren, a Ph.D. student at the University of Oxford in the United Kingdom, and Kyle Horton, a postdoc at the Cornell lab, built a computer model of weather and bird migration. They began with weather radar, the only effective way to monitor night-time migrations. Individual birds can't be detected, but radar can reveal the density of birds in the airspace: 60 to 70 birds per cubic kilometer in a light migration, and as many as 1700 in a heavy one.