The biggest bird in the world is actually the ostrich. An adult ostrich is actually very big. Some would be very big that it could be a heavy as 150 kilograms. Some ostriches are even bigger than human beings at 6 feet tall. Even though they cannot fly, they are known to be very fast whenever they need to run.
They have very strong legs that they use not only for running but also for attacking their predators. They do not need to consume a lot of water even though their size is huge. They can live without water for a few days. Ostriches are not known to live alone. They have to be a part of a group in order to thrive.