Q: Why do hummingbirds hum?

A: Because they don't know the words.

Wrong. A hummingbird's hum comes from its wings in motion, not from this tiny birds' vocal tract. In fact, hummingbird vocalizations are nothing to brag about, but the hummer is still one of the most amazing animals in the world.

There is just one species, the ruby-throated hummingbird, that spends its summers east of the Mississippi River in North America. Most of the 320 different hummingbird spcies live in South America. Fifteen of them do appear in North America, west of the Mississippi, and primarily in the Southwest.

Hummingbirds are the smallest birds on Earth, but in that tiny body, a little over three inches for the ruby-throat, is an awesome dynamo that enables hummers to fly great distances non-stop.

No, hummingbirds do not ride on the backs of geese. Our familiar ruby-throat commonly flies across the Gulf of Mexico during annual migration. Some ruby-throats winter in south Florida. The male ruby-throat weighs an average of 4.5 grams, including 2 grams of fat. It can fly non-stop for 26 hours on that small amount of fuel at an average speed of about 25 miles per hour. The non-stop range of a ruby-throat is about 650 miles.

Ruby-throated hummingbirds migrate from late May to early June and are nest-building by the summer solstice (June 21). The nest is built from plant down and spider silk and is affixed to saddle a horizontal branch. The nest's exterior is covered with lichens so that it looks like a two-inch lump on the branch.

Hummers also use manmade materials for nest-building--carpet fibers, pieces of twine and yarn are all seen in hummingbird nests. Hummers have been observed robbing building material from other birds' nests for use in their own.

It should be no surprise that hummers lay the world's smallest eggs. One Jamaican variety, the Vervain Hummingbird, lays an egg that is only 10 millimeters long. That is smaller than most adults' smallest fingernail.

During courtship ritual, the male flies from side-to-side while clucking at the female which sits on a branch to watch the show--if she is interested.

Flight is the hummer's most eye-catching behavior, especially since hummers can hover and fly backwards. The entire family has evolved special muscle configurations to accomplish these feats. The keel, that portion of the chest bone where flight muscles attach, is the largest of all birds when compared to overall body size.

Unlike most birds, hummers get lifting power from both the upward and downward stroke of their wings. They are able to rotate their wings at the shoulder to get lift on both strokes. This ability has been compared to variable pitch rotors on helicopters.

A ruby-throated hummingbird has only 940 feathers compared to the 25,216 feathers on a whistling swan; however, the hummer has more feathers (335) per gram of body weight than the swan. Biologists see this as an adaptation to retain body heat, as smaller body mass requires more insulation.

Hummingbirds will overwhelm feeding stations, and that's where most humans get to see them. Commercial feeders are usually made of red plastic and filled with boiled sugar water. There is no wide agreement on whether or not sugar water is a good replacement for flower nectar. However, most commercial "nectar" made for hummers contains artificial dies that may be harmful to the birds.

Hummingbirds feed by hovering in front of a flower, sticking their long bills deep inside, and lapping up nectar with a long, tubular tongue. Their tongues are covered with a rough surface to help collect flower nectar.

If you want to attract hummingbirds, plant plenty of red flowers in your yard. Hummers love red and will always inspect anything that color. Hollyhocks are favorite flowers, as are blossoms on squash, gourd and pumpkin vines. Put your first feeder near the flowers. You can move it to the house window once birds begin to use it.

The next time you see one, remember that you're looking at one of the most unusual animals alive and that the tiny creature you enjoy so much may have flown across the Gulf of Mexico to feed in your back yard.

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