There are numerous species of Hummingbird, spread throughout America. The smallest, the Bee Hummingbird, is the smallest bird in the world. They are named for the whirring, humming noise made by their wings in flight. Hummingbirds have an exceptionally fast metabolism, faster than and other vertebrate - their heart can beat 1,260 times per minute. This requires a large intake of high energy food to sustain it, and every day a Hummingbird will consume more than his own weight in nectar. At night, or when food is not available, he will slow his metabolism and enter a torpor state.