Stand near a hummingbird feeder and the bird arrives as a sound before it is a shape. A dry, electric hum, and then a body the size of your thumb hanging in the air on wings you cannot quite see. The wings are not invisible. They are simply moving too fast for your eyes to freeze them, the same blur of speed that trails a cheetah at a full sprint. So how fast do hummingbirds flap their wings, and how do they manage the one trick almost no other bird can do, holding perfectly still in midair?

About 70 beats a second, and over 200 in a dive

A hummingbird beats its wings about 70 times every second in ordinary flight, and more than 200 times a second when a courting male throws himself into a high-speed dive (Smithsonian's National Zoo). Seventy times a second is faster than you can say the word "second," repeated, before the wing has already gone up and down dozens of times.

That speed is why you hear a hummingbird before you understand what you are looking at. The hum is not a side effect of the flight. The hum is the flight, the wings beating the air often enough to make a musical pitch, the way a bee or a fast fan does. The same engine pushes the whole bird along at close to 30 miles per hour in level flight, and past 45 in a dive (Smithsonian's National Zoo).

The wings don't flap, they row

Here is the part that makes hovering possible. Most birds get their lift from the downstroke and treat the upstroke as a recovery, a quick reset before the next push. A hummingbird does something stranger. Its wings rotate at the shoulder and sweep through a figure-eight, pushing air forward, backward, and down, so they make lift on both the forward and the back stroke (Science World).

Think of it less as flapping and more as rowing, or treading water in the air. Because no part of the stroke is wasted, the bird can hang in one spot indefinitely. By adjusting the angle of its wings and tail it can hover, slide backward, pivot to either side, even tip briefly upside down (Science World). It is the only vertebrate that can keep up sustained hovering at all (Smithsonian's National Zoo). It is closer to a tiny helicopter than to a sparrow, and it solves the same lift problem that keeps an airplane up, just by moving the wing instead of the whole aircraft.

The engine behind the blur

A motion that fast burns a frightening amount of fuel. A hummingbird's heart runs from around 225 beats a minute at rest to more than 1,200 beats a minute when it is flying (Smithsonian's National Zoo). To keep that furnace lit, it drinks roughly 80 percent of its body weight in nectar every single day, which works out, for a creature our size, to a 150-pound person drinking close to a hundred 20-ounce sodas (Smithsonian Magazine).

That is why a hummingbird never seems to rest at a flower for long. It is on a relentless circuit, and as it drinks it carries pollen from bloom to bloom, doing the same quiet work bees do when they collect nectar. The wing speed and the appetite are two sides of one bargain: an animal that lives this fast has to eat almost constantly to pay for it.

Switching the engine off at night

The bargain has a catch. A body that burns this hard cannot survive a cold night the way it survives a warm day, because it would run out of fuel hours before sunrise. So a hummingbird does something close to switching itself off. It enters torpor, dropping its body temperature nearly to the surrounding air, breathing only now and then, almost comatose, in a sleep so deep it can cut its hourly energy cost by up to 95 percent (Smithsonian Magazine).

So the blur you cannot quite see at the feeder is a body living at the very edge of what a warm-blooded animal can do, a heart near 1,200 beats a minute, wings near 70, an engine that has to nearly stop each night just to make it to morning. The hummingbird is one of those animals that seems to break the rules of its own size, the way an animal that may never die of old age does. The next time one hangs in front of you, remember that you are watching the fastest, hungriest, most expensive way there is to be a bird.

Keep wondering: those beating wings solve the same puzzle that keeps an airplane in the air; the nectar a hummingbird chases is the start of why bees make honey; and for another animal whose body does something physically absurd, see how hard a mantis shrimp punches.