Hummingbirds, the smallest birds in the world, are fascinating and beautiful creatures. They have the highest metabolic rate of any animal with a heart rate of over 1,200 beats per minute. Their wings may beat 50-80 times per second (their wings do not flap but rather bend & flex in a rotating motion, producing the humming sound from which they take their name). Hummingbirds are also the only bird that can fly in any direction, including backwards and upside-down!
Require Constant Food Source
In order to maintain this immense output of energy they must consume half of their own weight each day. In fact, in order to survive the night without feeding they slow their metabolic rate to a near hibernation state and lower their heart rate to around 100 beats a minute. They feed primarily on nectar but also rely heavily on small insects in their diet to provide protein and to feed their young.