Can Hummingbirds Fly Backwards? How Hovering Works

How do hummingbirds fly backwards?

Most birds flap their wings up and down, getting nearly all of their lift on the downstroke and folding their wings on the way up. Hummingbirds do something different. When hovering, they hold their body upright and sweep their wings forward and back in a nearly horizontal plane, like oars sculling through the air.

At the end of each forward sweep the wing flips over, so its leading edge still faces the direction of travel on the return stroke. Seen from the side, the wingtip traces a flattened figure-eight. Because the wing meets the air at a useful angle in both directions, both strokes push air downward and keep the bird aloft.

To fly backward, the bird tilts its body and the plane of its wingbeat slightly back, so part of the force pushes it rearward instead of only up. A ruby-throated hummingbird uses this most often to back out of a flower after drinking, rather than turning around in a tight space.

The shoulder joint that makes it possible

The secret lies in the hummingbird’s skeleton. Its upper arm bone (humerus) and forearm are very short, while the “hand” bones that support the main flight feathers make up most of the wing. The elbow and wrist joints are held nearly rigid, so the whole wing works as a single stiff blade.

All the movement happens at a highly mobile shoulder joint. It lets the wing rotate almost 180 degrees around its long axis, which is what allows it to turn over between strokes. Large flight muscles, about a quarter to a third of the bird’s weight, power both strokes. The muscle that raises the wing, the supracoracoideus, is proportionally much larger than in other birds because it does real work on the upstroke.

Lift on both strokes: how hummingbirds differ from insects

Scientists once assumed hummingbirds hovered exactly like insects, making equal lift on both strokes. Wind-tunnel studies of rufous hummingbirds, which tracked tiny particles in the airflow around the wings, showed something in between birds and insects. About 75% of the lift comes from the downstroke and about 25% from the upstroke.

That upstroke share is small compared with an insect’s, but it is something no other bird manages in sustained flight. It is enough to let hummingbirds hold position in still air, which is why scientists describe their flight as a halfway point between typical birds and insects.

Sideways, up, down and upside down

Hummingbirds can move in almost any direction from a hover: forward, backward, sideways, straight up and straight down. They can also rotate on the spot and stop dead from fast forward flight. These skills let them feed at dangling flowers, chase rivals and dodge predators.

Popular claims that hummingbirds “fly upside down” are exaggerated. They can flip, roll and twist extremely quickly during chases, and in high-speed video they sometimes turn briefly at strange angles, but they do not cruise upside down. Hummingbirds can even shake rain from their feathers in midflight, twisting their head and body in a fraction of a second while staying airborne.

How much energy does backward flight take?

Hovering is extremely costly, and hummingbirds burn energy faster than almost any other animal while doing it. Their wings beat dozens of times a second, as described in how fast do hummingbird wings beat?

Surprisingly, flying backward does not seem to be harder. Experiments in which Anna’s hummingbirds fed from a feeder while the air flowed toward them, so they had to fly backward to stay in place, found the energy cost was similar to hovering. The birds kept their bodies more upright and adjusted their wing motion to make the reverse flight efficient.

Can other birds fly backwards or hover?

Some birds can hover briefly. Kestrels and some hawks “windhover” by facing into the wind, terns and kingfishers hover before diving for fish, and sunbirds in Africa and Asia occasionally hover at flowers, although they usually perch to feed. None of them can hover in still air for long or fly backward on purpose.

Flying backward is a real hummingbird specialty. Other birds may slip backward for an instant when braking, landing or being pushed by wind, but only hummingbirds can steer in reverse. Bats, which fly in a very different way, are compared with birds in bat vs bird.