Summer thrums.

Life is ascendant under the summer sun, endlessly cycling in little eddies cast up in the wake of successively larger cycles of seasons, planets, stars, and galaxies. Each cycle has its own frequency, its own back and forth, hither and yon, its own signature in the guest book of eternity.

Einstein observed, “Everything in life is vibration,” which makes sense when you think about the pulsing physics of subatomic particles. If everything in life is vibration, then everything has a frequency, like the tone produced by a guitar string or piano wire. Summer days are strung tightly across the long heated expanse between dawn and dusk, relaxing only slightly through the night.

You can hear the tension of it everywhere, in the cicada’s song, in the caustic caw of the crow, in the whine of tire treads incessant on the interstate.  And in the afternoon heat on our back terrace, you can hear it humming in the honeysuckle.

A female ruby-throated hummingbird has claimed the flowering shrub that has scrambled up and over a rock wall. I usually hear her before I see her. She beats her wings 53 times a second – a frequency of 53 Hz, which on a piano would be a slightly flat A two octaves below middle C. Beating at that rate, her wings are a blur, yet she controls them with such great precision that she can fly at top speed (about 35 mph) and come to a full stop instantaneously to hover, motionless in mid-air, or move up or down, or, uniquely, backwards.

If this hummer in the honeysuckle had a tachometer, it would be constantly in the red zone during flight. She weighs less than a nickel, but like all hummingbirds in flight, she has a metabolism that burns brighter and faster than all other animals. In flight, the heart rates of hummingbirds can exceed 1,000 beats per minute. To power that little dynamo, they consume more than their own weight in nectar each day and concentrate only on flowers with a sugar content of greater than 10 percent. Their diet isn't all sweets, though. They get needed nutrients from eating insects.

Hummingbirds burn energy in flight at a rate 15 times higher than when they are perching. Consequently, they spend about 75 percent of their time resolutely sitting in trees. We rarely see them there because they are so still and so small. Their extraordinary energy requirements relative to their size, however, make this conservation tactic of just sitting around essential to their survival. Without it, they would starve to death in the night.

For a creature that is always just a step ahead of its brightly burning metabolic fuse, it seems incredible that in the late summer and fall, ruby-throated hummingbirds migrate across the Gulf of Mexico - a 500-mile non-stop trip across open water. How is that even possible? Researchers have found, however, that prior to this feat, the birds double their body mass with stored fat, which they burn off during the trip.

For now, though, this female ruby-throat joins in the ever-cycling summer thrum on our back terrace, where I am just sitting around - not for the sake of survival. In the summer heat, my purposes are more dissolute than resolute. But I am grateful that the life cycles of the man burning too few calories and the bird burning too many intersect in this way before we are carried off in our respective eddies toward eternity.

(More than 90 Field Notes essays by Curtiss Clark can be found at www.field-notebook.com.)