Migrating birds move more mass than all global aircraft

Meteorologists once puzzled over strange, ghost-like rain bands appearing on their radar screens during clear nights. These artifacts turned out to be the pulse of a planet in motion as more than 500 million birds cross the United States in a single night. This biological traffic moves between 300 and 1,500 meters above the ground, effectively turning the lower atmosphere into a dense, living layer of biomass. The collective weight of these travelers is so immense that it far exceeds the mass of every commercial and private aircraft currently in the sky.