A flash of sapphire, a flutter of wings, and the tiny bird—or was it an insect?—vanishes, the briefest mirage. Moments later it reappears, this time at a better angle. It's a bird all right, a thumb-size dervish with hyperkinetic wings that can beat 80 times a second, producing the faintest hum.

Even reserved scientists can't resist such words as "beautiful," "stunning," and "exotic."

A greater wonder is that the seemingly fragile hummingbird is one of the toughest beasts in the animal kingdom.

Its cranberry-size heart, which averages 500 beats a minute (while perching!), would have thumped four and a half billion times, nearly twice the total for a 70-year-old person.

Yet these little birds are durable only in life. In death their delicate, hollow bones almost never fossilize.

"They're a bridge between the insect and bird worlds,"