How do schools of fish or flocks of bird manage to flow in the same direction while changing it so fast?

Question

How do schools of fish or flocks of bird manage to flow in the same direction while changing it so fast?

Answer 1

There are several factors that can influence this.  The first is the detection of a predator or prey, which can be visual, auditory, or olfactory.  Second, animals have forms of communication that humans are not always aware of.  Animals can communicate through the use of pheromones (chemical signals), body language, and other sounds that represent different ideas and concepts.  Third, groups of fish and birds often times have leaders, or dominant members of the flock/school, that the other members naturally follow.