Nature Notes: Lucy in the Sky With Diamonds

MARSHA SPARKS photo

At first glance, hummingbirds seem capable of almost magical flight; hovering motionless one second, and then tracing huge arcs across the sky over and over. In truth, captured on high speed film and then viewed at a much slower pace, the amazing aerobatic flight of hummingbirds becomes even more fantastic.

For starters, the weight of hummingbirds compared to their wing span, and the viscosity (thickness) of the air compared to their small size, all blend together to allow hummers to fly through the air in a manner somewhat similar to the way we humans can maneuver in water. Our large body weight/size ratio compared to that of the tiny hummingbird makes the viscosity of air to hummingbird flight similar to water for us as we swim in it.

A hummingbird can push away from a perch-style feeder and travel for several body lengths in the air before it has to start flapping its wings, much the same way as you or I might push away from the edge of a swimming pool and "coast" for several feet before we have to start swimming.

Again, due to the weight/lift ratio of hummers, they can hover in one place much easier and with much less energy consumption than you might think. They get great MPG: miles per geranium!

Think back to the pool. It's not too hard to tread water for a few seconds or even a minute or two, and it's pretty much the same for hummers as they're just treading air instead.

Boat propellers work much better in water than in the air simply because they are designed to move a much denser medium. What works in water won't work in the air, and that's why airplane propellers make lousy boat props.

The eagle is not a particularly great flyer if it must rely solely on flapping its wings for lift. It is simply too big and too heavy and to the eagle, the air seems very thin. But the hummingbird excels in its thick air, able to pause mid flight and look a flower squarely in the eye or pick off a gnat in mid flight (the gnat feels like it is flying in honey).

Like the debate that raged about whether or not a horse was ever completely off the ground as it ran, or if an elephant gets two feet off the ground at the same time, only with high speed photography does the truth come out.

Nature has some marvelous moves, many of which are simply too fast for us to see easily. But as we discovered from the hummingbird, all is not as it seems. When we see the hummer as a pilot who floats much easier in the sky than we do, it is somewhat easier to grip the emerging new concept that hummers may be circling the continent in their migrations generation after generation.

New data suggests that like the monarch butterflies, some hummer species may travel routes many years in length and the offspring of the hummers may complete the loop to a destination they may have never have seen before, partly because they can fly easier than just about everyone else. Except maybe for monarchs or tiny ballooning spiders.

• Check out our new weekly nature movie at: http://home.pacifier.com/~sparks /wildlife!!.html

• Craig Sparks is director of NAWA, a filmmaker, freelance writer and wildlife rehabilitator.

• Found injured wildlife? Questions? Call The wildlife center at 665-3595 or send an e-mail to: sparks@pacifier.com.

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