hummingbirds are the world's smallest birds. the bee hummingbird of cuba is only 2 inches long. this is just a little bigger than a penny. hummingbirds live only in the western hemisphere. most migrate north in the early spring and return south in early fall. their life span is between nine and twelve years. the colorful bird are very curious. they are also aggressive toward each other. perhaps their best know trait is their ability to fly backwark. they are the only bird in the world that can do this.