The ruby-throated hummingbird is the only hummingbird found east of the Rockies (apart for the buff-bellied hummingbird which is rarely found on the Gulf coast of Texas and Louisiana). This bird is about 3½ inches long and only weighs about 2½ grams or as much as 2½ paper clips. The back is metallic green while the ruby throat is only found in males. Hummingbirds are attracted to red flowers and have long thin beaks for feeding off nectar, but they also eat insects. The bird in the photograph is feeding from a cardinal flower which contains no nectar, so it must be searching for insects. The photograph also illustrates how the bird can hover in one spot as the image of head and body is sharp while the wings are blurred.

Hummingbirds are skilled fliers and can even fly backwards so that they can move from one flower to another without turning around. The males also give a U-shaped courtship display which may go as much as 40 feet up and down. Hummingbirds, particularly males, are very territorial and aggressive towards each other. In late August, hummingbirds start feeding heavily so as to store fat for their migration of about 1,000 miles across the Gulf of Mexico. They become noticeably plumper and almost double their body weight.

Hummingbirds are named for the sound of their rapid wingbeat, but they also have a mouse-like twittering song.