HUMMINGBIRDS OCCASIONALLY SAMPLE MY FRONT-YARD PLANTINGS, much to my amazement of their aerial capabilities. Indeed, this ain’t the half of it as I learned from Bob Holmes in “Hummingbirds Thrive on an Extreme Lifestyle. Here’s How.” knowable magazine, September 25, 2024.
“Everyone loves to watch hummingbirds,” Holmes describes, “— tiny, brightly colored blurs that dart about, hovering at flowers and pugnaciously defending their ownership of a feeder. But to the scientists who study them, hummingbirds offer much more than an entertaining spectacle. Their small size and blazing metabolism mean they live life on a knife-edge, sometimes needing to shut down their bodies almost completely just to conserve enough energy to survive the night — or to migrate thousands of miles, at times across open ocean.”
“Their nectar-rich diet,” Holmes says, “leads to blood-sugar levels that would put a person in a coma. And their zipping, zooming flight sometimes generates g-forces high enough to make a fighter pilot black out. The more researchers look, the more surprises lurk within those tiny bodies, the smallest in the avian world.”
Here are other tidbits gleaned from Holmes’ article together with my usual Internet sleuthing.
The Basics. Wikipedia writes, “Hummingbirds are birds native to the Americas and comprise the biological family Trochilidae. With approximately 366 species and 113 genera, they occur from Alaska to Tierra del Fuego, but most species are found in Central and South America.”
“Hummingbirds,” Wikipedia continues, “have varied specialized characteristics to enable rapid, maneuverable flight: exceptional metabolic capacity, adaptations to high altitude, sensitive visual and communication abilities, and long-distance migration in some species. Among all birds, male hummingbirds have the widest diversity of plumage color, particularly in blues, greens, and purples. Hummingbirds are the smallest mature birds, measuring 7.5–13 cm (3–5 in) in length.”
Trinidad and Tobago hummingbirds. Image by Charles J. Sharp from Wikipedia.
Etymology. “They are known as hummingbirds,” Wikipedia states [the obvious…] “because of the humming sound created by their beating wings, which flap at high frequencies audible to other birds and humans. They hover at rapid wing-flapping rates, which vary from around 12 beats per second in the largest species to 80 per second in small hummingbirds.”
Nectar High. Bob Holmes recounts in knowable magazine, “To fuel their sky-high metabolic rate, hummingbirds suck down about 80 percent of their body weight in nectar each day. That’s the equivalent of a 150-pound person drinking nearly a hundred 20-ounce Cokes daily — and nectar is often much sweeter than a soda.”
A Metabolic Flip. Ken Welch, a comparative physiologist at the University of Toronto at Scarborough, describes a metabolic flip from sugar to fat: “By the end of its nightly fast, a hummingbird has nearly depleted its sugar stores—which poses a metabolic challenge: How does it wake up and fly? There’s nothing but fat available to burn.”
Holmes learns from Welch, “Hummingbirds have evolved to be remarkably nimble at switching their metabolism from sugar-burning to fat-burning, he has found. ‘This requires an enormous shift in the biochemical pathways that are involved,’ Welch says—and it happens in mere minutes, far more quickly than other organisms can manage. ‘If we could have that kind of control over our fuel use, we’d love that.’ ”
Holmes says, “Other as yet unknown strategies to cope with high blood sugar may one day yield practical benefits for managing diabetes in people. ‘There could be a gold mine in the genome of the hummingbird,’ says Welch.”
Seasonal Work Loads. Physiological ecologist Anusha Shankar describes to Holmes a hummingbird’s seasonal changes in energy usage: “We ended up finding that it’s super variable,” Shankar says. Holmes describes, “During the early part of the summer when flowers are abundant, birds could meet their daily energy needs with as little as a few hours of feeding, spending as much as 70 percent of the day just perching, she found. But when flowers became scarcer after the arrival of the summer monsoon rains, birds at one site perched just 20 percent of the time and used the rest of the day for feeding.”
And a Good, Deep, Night’s Sleep. “Hummingbirds have a trick,” Holmes says, “to help them eke out their energy reserves: When a bird is in danger of running out of energy, it may go torpid at night, dropping its body temperature nearly to that of the surrounding air—sometimes just a few degrees above freezing. While in torpor, the bird appears almost comatose, unable to respond quickly to stimuli, and breathing only intermittently.”
Holmes continues, “The strategy can save up to 95 percent of hourly metabolic costs during cold nights, Shankar has calculated. That can be essential after days when a bird has fed less than usual, such as after a thunderstorm. It also helps birds save energy to pack on fat before migration.”
Hummingbirds can fly backwards, perch up upside down, and even hibernate. Image by KELLYPLZ/POND5 via knowablemagazine
Many hummingbirds can enter a state of torpor, a form of hibernation in which they let their body temperature drop to near that of the air.
Just what we all could use when a sugar high wears off: a nice nightly torpor. ds
© Dennis Simanaitis, SimanaitisSays.com, 2024