Hummingbird, this is the world's smallest bird. This is the lightest warm-blooded creature in existence. In fact, scientists argue that there cannot exist any warm blooded species that can be lighter than hummingbirds. This bird can beat its wings 50-200 times per second, this is an extremely terrible number. In addition, this bird is the only bird with a flap of wing 8, so the bird can fly in midair, fly to the sides, fly diagonally or fly backwards.