How nectar bats fly nowhere
The first direct measurements of wingbeat force show how hard hovering is
By Susan Milius
Flying forward is hard enough, but flying nowhere, just hovering, is so much harder. Most bats and birds can manage the feat for only a few frantic seconds.
Hovering means losing a useful aerodynamic shortcut, says aerospace engineer and biologist David Lentink of Stanford University. As a bat or bird flies forward, its body movement sends air flowing around the wings and providing some cheap lift. For animals on the scale of bats and birds, that’s a big help. Without that boost, “you’re going to have to move all the air over your wings by moving it with your wings,” he says. The energy per second you’re consuming to stay in place by flapping your wings back and forth like a hummingbird “is gigantic.”