The ability to fly has developed independently many times throughout the history of the Earth. Flying, Running, and Swimming The fastest running bird is the ostrich, but it cannot fly. The ostrich is also the fastest two-legged runner of all the animals on Earth. The ostrich is the largest bird. Some birds cannot fly .
Most birds can fly.
Flying birds' wings are shaped to provide lift, allowing them to fly . Male birds are frequently more brightly colored than females. This is to attract females for mating purposes. Feathers are highly modified scales. There are different types of feathers that have different uses.