Most birds produce substantial upward force—aka lift force—only with the downward flap of their wings. The secret to the hummingbird's hovering ability lies in the near symmetry of its wing motion, which allows it to produce lift during the upstroke as well as the downstroke. By filling the air with a fine mist using an ultrasonic fogger, researchers can observe the tornado-like vortices that this Anna's hummingbird sheds at the end of each half-stroke—when its wings flip more than 90 degrees and reverse course.SOURCES: VICTOR ORTEGA-JIMENEZ AND ROBERT DUDLEY, UC BERKELEY; DOUG ALTSHULER, UNIVERSITY OF BRITISH COLUMBIA, VANCOUVER. Photographs by Anand Varma / National Geographic
Hummingbirds often brave downpours to gather the nectar needed to avoid starvation. This Anna's hummingbird shakes off rain as a wet dog does, with an oscillation of its head and body. According to researchers at UC Berkeley, each twist lasts four-hundredths of a second and subjects the bird's head to 34 times the force of gravity. Even more remarkable: Hummingbirds can do this in flight as well as when perched.SOURCES: VICTOR ORTEGA-JIMENEZ AND ROBERT DUDLEY. Photographs by Anand Varma / National Geographic
