No. 2903: HUMMINGBIRDS
by Andrew Boyd
Today, life as a blur. The University of Houstonís College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.
My chance encounter was as exhilarating as it was surprising. Our eyes met, and I feared my wild companion would flee in fear, having come within armís reach of me. But instead, he stayed, tilting his head one way then another as he examined me. After what seemed both forever and just an instant, he darted away with almost unnatural agility.
Female Ruby-throated Hummingbird
Iíd later learn my run-in wasnít unique. Hummingbirds are curious, and always in search of sugar-bearing nectar. Thatís a necessity — a byproduct of the way nature engineered these captivating creatures.
Itís believed that hummingbirds evolved in response to an abundance of nectar-laden plants many millions of years ago. This rich source of energy was tapped only by lightweight insects. Nature responded with the nimble hummingbird. Hummingbirds donít burden a fragile flower with their weight, but instead hover in place while sipping nectar. To do that, natureís had to take on a variety of design issues, balancing each in just the right way.
If youíre like me, you learned to tread water by moving your outstretched arms back and forth, adjusting the angle of your hands on the forward and backward strokes. Hummingbirds do something quite similar. But since theyíre treading air instead of water, they need more than just a specialized stroke.
Hummingbirds are of necessity tiny. The smallest species weighs less than a dime; the largest — the "giant hummingbird" — weighs only as much as two half dollars. Yet these lightweights still require a lot of flapping to stay in place — up to a hundred times per second. If you come face to face with a hovering hummingbird you donít actually see wings, you see a blur. This combination of stroke, speed and low body weight not only allows hummingbirds to remain stationary, but to fly straight up and even backward. These are tricks of which no other birds can boast.
But this agility comes at a price. Everything about hummingbirds is exaggerated. To stay alive a hummingbird must eat more than its own weight in food each day. And to convert it to energy, hummingbird metabolism is off the charts. Their hearts can beat over twenty times per second, though they have the ability to drastically slow that when at rest. And it proves a lifesaver — literally. If the heart maintained the same rate at sleep as when active, a hummingbird would die of hunger in a matter of hours. Even so, life in the fast lane takes its toll. A typical hummingbird lives only about five years.
Itís amazing when you stop and think about the delicate balance evolution has engineered in hummingbirds. But itís even more amazing to see these spectacles of nature as they go about their business pollinating flowers in return for a sip of sweetness; brilliant stars of the garden shining ever so brightly, yet with us only so briefly.
Iím Andy Boyd at the University of Houston, where weíre interested in the way inventive minds work.
Notes and references:
Actual wing flap and heart rates vary from species to species. One-hundred flaps per second is at the upper limit, with many of the more common species ranging in the neighborhood of twenty to thirty. A heartbeat of twenty beats per second is also at the upper limit. Hummingbirds have been known to live for over a decade, but of those that make it past their first year, the average lifespan is generally thought to be roughly three to five years. Many species of hummingbird must eat many times their body weight in food each day to stay alive.
L. Forsberg. Flying Jewels. Alaska Airlines Magazine, August, 2013, pp. 50-59.
All pictures are by John Lienhard.
For many more hummingbird pictures, see http://enginespics.smugmug.com/Animals/Birds/Ruby-throated-Hummingbird/25896230_W6m6fp#!i=2146081008&k=hzCDgvx. Accessed September 4, 2013.
This episode first aired on September 5th, 2013.