In Ecuador’s Chocó Andino de Pichincha Biosphere Reserve, a 709,192-acre biodiversity hotspot northwest of Quito, hummingbirds thrive. The country is home to roughly 132 of the world’s 320-plus hummingbird species. On a single afternoon in the reserve’s Mashpi Cloud Forest, you might see a couple dozen of these species, from tiny green thorntails to velvet-purple coronets. 

The brilliant-colored avians dart and whizz between feeders, flying forwards, backwards, and in some cases, upside down. They’re dazzling to watch, but also incredible to hear. Their soft hums sound like little motors that, together, create a sort of natural symphony. But where does this distinct “buzz” come from? Or, to put it more bluntly, why do hummingbirds hum? 

To find out more about hummingbirds and their iconic sound effects, Popular Science turned to Tatiana Santander, a senior project coordinator for Aves y Conservación (Birds and Conservation), which conducts research and environmental education projects in Ecuador’s Mashpi Reserve. 

What are hummingbirds?

Hummingbirds are small, colorful avians native to the Americas. They’re incredibly unique. These tiny, fast-flying birds feature specialized anatomy, an ultra-quick metabolism, and one-of-a-kind flight mechanics that all result from coevolution: a reciprocal process when two or more species continuously adapt to each other. In this case, hummingbirds and flowers. 

“For example,”  says Santander, “hummingbirds have evolved with long bills and a long tongue that is bifurcate,” or split in two. These features make it easier for hummingbirds to feed on nectar from flowers that specifically fit their elongated beak and specialized tongue. At the same time, the flowers’ tubular shapes keep most insects from getting to the nectar first. 

Hummingbirds have also developed a distinct flight pattern to feed on brightly colored, nectar-rich blooms like salvia and tiny blue vervain. It’s another example of coevolution. 

“Hummingbirds are the only birds that can fly in all directions, even backwards,” says Santander. They also hover to eat. “Many hummingbirds can flap their wings over 80 times per second. It’s crazy!” In contrast, an average bird—like a gull or a sparrow—flaps its wings much slower: typically between three to 15 times per second, depending on the bird’s size. 

See Hummingbirds Fly, Shake, Drink in Amazing Slow Motion | National Geographic

Hummingbirds are the only birds that can fly backwards. Video: See Hummingbirds Fly, Shake, Drink in Amazing Slow Motion, National Geographic

“This kind of life, the constant hovering,” says Santander, is very demanding on hummingbirds’ metabolisms. “Their muscles need a lot of oxygen,” she says, “so they have to keep eating all day.” 

The sugar-rich nectar they consume delivers food directly to their flight muscles, where cell parts known as mitochondria use oxygen to break down the sugar and generate energy. In fact, hummingbirds consume half to multiple times their body weight daily. Along with nectar, this includes tree sap and small insects. “This is like if we [would] eat about 300 hamburgers a day!”

Rather than flapping their wings up and down like most birds, hummingbirds rotate their wings in a constant figure-eight motion. They also have flexible shoulders that allow them to turn their wings nearly 180 degrees. Think of them like little biological helicopters. 

By continuously changing the angle of their wings, hummingbirds create pressure differences akin to miniature tornado-like vortices of air. These generate the lift (a.k.a. the upward force) and thrust—the ability to move forward—they need to hover, fly, or even stay stationary. In contrast, most birds only get lift by pushing their wings down. 

Why do hummingbirds “hum”?

It’s this rapid shifting of air pressure that creates a hummingbird’s distinct “hum.” This signature buzzing sound differs from the “woosh” that you’ll hear from larger birds, like swans or geese. Instead, hummingbirds’ buzzing creates one, continuous acoustic tone that varies according to the specific species. 

“The hum is because of the rapidity of a hummingbird’s wingbeats,” says Santander. Each species moves its wings at different speeds—ranging from roughly 40 to 200 beats per second. These swift movements cause overlapping acoustic frequencies to create a complex, layered hum. 

A hummingbird’s sound can also vary depending on the size of the bird, its wing size, and its movement. For instance, a medium-sized broad-tailed hummingbird creates an almost insect-like, metallic trill with its wings, which beat approximately 50 to 60 times per second. 

On the other hand, the giant hummingbird operates more like a normal bird, flapping its wings only 10 to 15 beats per second. This creates a sound that’s deeper, like the dull whirring of a helicopter. 

Extremely tiny woodstar hummingbirds have to flap their wings 80 to 100 times per second in order to stay hovering. Their rapid wingbeats produce a distinct buzzing sound that’s often compared to a bumblebee. 

Beyond the “hum”

Beyond the familiar wing hum, hummingbirds make other unique sounds using their wings, feathers, and movements. 

“Hummingbirds are territorial,” says Santander. “Sometimes, when they are fighting with others, they make a sound, like a pump, when they flap their wings.” The birds will change the frequency of their wingbeats, as well as the angle of their wings, which alters the air pressure around them, to create this unique sound. 

The Sounds of Hummingbirds

The rapid shifting of air pressure from a hummingbird’s wings creates their distinct “hum.” Video: The Sounds of Hummingbirds, WKU PBS

“Or when we see a hummingbird flying, we might hear something like a fast boom.” This is often the result of a high-speed, male courtship dive. For example, when a male Anna’s hummingbird plunges downward to attract a female, he reaches speeds of up to 60 miles an hour. 

After diving for about 130 feet, the bird abruptly pulls upward, allowing air to rush across his fanned-out tail feathers and causing them to vibrate like violin strings. This creates a loud acoustic “pop” that scientists have compared to a miniature sonic boom. 

Hummingbirds are true originals

Santander’s favorite hummingbird is the black-breasted puffleg. Known for its distinct leg plumage, this tiny avian flaps its wings between 50 to 80 beats per second, creating a high-pitched buzz that sounds almost mechanical. 

“It’s an endangered species and endemic to Ecuador,” says Santander. At Aves y Conservación, “we’ve been studying and implementing conservation efforts to conserve this species.” But ultimately, Santander loves all hummingbirds. 

“There was a famous researcher in Ecuador who was a leader in hummingbird studies,” says Santander, referring to ornithologist Fernando Ortiz-Crespo. In his book, Los Colibríes: Historia natural de unas aves casi sobrenaturales (Hummingbirds: The Natural History of Almost Supernatural Birds), Ortiz-Crespo “describes hummingbirds as ‘almost supernatural!’ Sometimes they really do seem like they’re from another world.”

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