The secret to birds’ flight starts with the shape of their wings. They’re curved in a way that causes air to flow more slowly under the wing than above it. That creates an area of low pressure just above the wing that pulls the bird up into the sky—a force called lift. Airplane wings are curved in a similar way — but unlike airplanes, bird wings don’t stay in place, they flap! That lets birds push their way into the air from a dead stop. On the upstroke of a wing-flap, birds fold their wings inward, reducing drag on the wing.More info and transcript at BirdNote.org. Want more BirdNote? Subscribe to our weekly newsletter. Sign up for BirdNote+ to get ad-free listening and other perks. BirdNote is a nonprofit. Your tax-deductible gift makes these shows possible.