The tiny bird is engaged in its improbable hovering flight. The wing beats are a blur, vibrating the still afternoon air into an incessant buzz. I watch the hummingbird insert its needle-bill into the heart of an orange jewelweed flower, where the pedicels of the blossom part as the bird edges in.

The ruby-throated hummingbird (Archilochus culubris) is rewarded with a drop of pure nectar. The flower benefits, too, by depositing a cap of pollen onto the head of the bird. At the next blossom, more nectar is yielded and cross-pollination occurs.

We planted wild jewelweed (Impatiens capensis) alongside the ramp to our backyard deck to have a handy natural remedy for mosquito bites. The perpetually damp, shady spot at the foot of the downspout is the perfect habitat for this streamside plant. The plants are flourishing, providing us with relief from the omnipresent tiger mosquito.

This summer's drought has turned many Maryland farm fields a sickly brown, but the rain barrel attached to our gutters provides an ample supply of water for the hibiscus and mandevilla on the deck.

We tend the cultivars with care, and they reward us with showy flowers that attract the ruby-throats. But when the stand of jewelweed started to blossom in late summer, though, it quickly eclipsed the nursery plants as the hummers' favorite.

Ruby-throated hummingbirds delight backyard birdwatchers. They readily come to nectar feeders and flowers, defending their sources of food with remarkable aggression.

Although a dozen species are found in the western United States and along the Mexico border, the only hummingbird routinely found in the eastern part of North America is the ruby-throat. The bird's summer range edges into southern Canada. It winters in Central America.

As a family, hummers are the smallest of all birds. The ruby-throated hummingbird I'm watching is typical. It is less than 4 inches from the tip of its beak to the end of its tail. The bird weighs just one-tenth of an ounce.

His head, back and part of his tail is dark green. The characteristically short tail is edged in black with a narrow white border. Underneath is a gray-green belly, narrow white breast, and the iridescent ruby throat that gives the bird its name.

The throat patch is called the gorget. The iridescence is a function of the shape and composition of the feathers, which are composed of cells in a precise array that contain microscopic air disks. When viewed straight on, the normally black throat suddenly flashes into a ruby red.

Females and young lack this distinctive characteristic.

The male that I'm watching is a whirlwind of motion, darting from flower to flower. He has a remarkable metabolism, beating his wings at 53 strokes per second in a figure-eight pattern that allows him to hover and even fly backward. At rest, this bird's heart rate is a chest-exploding 250 beats per minute. When he's in flight, the count soars to 1,250. The ruby-throat's normal body temperature can be as high as 111 degrees.

To fuel this dynamo, the ruby-throat must consume extraordinary amounts of food. In addition to nectar, hummers consume tiny insects, especially spiders. They'll even rob spiders' nests of trapped insects. To add insult to injury, hummingbirds will also often use spider's webs to line their nests.

This hummingbird will be departing for Central America as soon as the first major cold front moves through. He'll take advantage of the prevailing northerly winds to speed his trip thousands of miles to the south. On the way, my ruby-throat will make multiple stops and likely conduct his trip largely over land.

The remarkable journey he's about to undertake, though, isn't as impressive as his effort to get to my backyard every April. On the spring trip north, he'll fly from the Yucatan Peninsula 600 miles nonstop over the open waters the Gulf of Mexico. He'll be in a competition to stake out breeding territory. Speed counts.

To prepare for the momentous flight, the ruby-throat will eat like there's no tomorrow. He'll add 10 percent to his body weight every day for a week, adding two grams of fat to his tiny three gram body. Imagine a 150-pound man ballooning to 255 pounds in just seven days! This extra fat is the fuel that the bird's remarkable metabolism will burn in its flight over the gulf.

I'm standing here trying to imagine how a tiny drop of nectar, hidden in the recesses of the jewelweed, can power such an unlikely bird over such astounding distances.

But why should that be such a foreign concept? Here I stand, a lone organism trying to find my way through the unpredictable journey of life, endlessly searching for a niche in this world that's a perfect fit.

And what could be more improbable than that?