The ostrich is the largest bird in the world. While this bird is unable to fly, it can run incredibly fast. An ostrich has legs that are lightweight and yet very sturdy, this enables the ostrich to run up to 35 miles per hour. That's faster than most of the other animals living on the African plains. You may also notice that the ostrich has sharply clawed, 2-toed feet. These help the animal defend itself when running isn't an option.