Hummingbirds are the smallest birds in the animal kingdom. The smallest hummingbird is the bee hummingbird, which is 2 inches long and weighs less than a penny.
Hummingbirds are able to hover in the air and fly backwards. This helps them to draw nectar out of their food plants more efficiently. Their wings beat so rapidly that they give off a humming sound, which gives the bird its name.
Many hummingbirds actually co-evolved with the flowers they feed on. Some hummingbirds' bills are elongated or curved to fit into the throats of the flowers they need. Some hummingbirds have to visit hundreds of flowers a day to avoid starving to death. Despite this, a hummingbird can live as long as 10 years. Hummingbirds of North America even undergo the rigors of migration to the Caribbean, Mexico and Central America to spend the winter.
The metabolism of the hummingbird is higher than any warm-blooded creature, and when they're not foraging, they go into a state called torpor. During torpor, their bodily functions slow down drastically. It is a state very much like hibernation.
In species of large hummingbirds, the males are larger than the females. In species of small hummingbirds, the females are larger than the males. The males of some species are brilliantly colored, with iridescent feathers. Some perform spectacular courtship flights to entice a female.