This video shows the amazing whorls and patterns made by a flock of starlings. You might see these over cities. These displays used to be common over London, and I think still are over Rome.
Whilst there has been much scientific research and theories on why starlings do this, the contention is that the birds use a simple algorithm that states that they have to stay a certain distance away from their nearest neighbours, and hey presto this amazing display can take place.
I am not happy with this theory. I believe that the birds give up their own identities and merge themselves into a flock supra-identity. The actions and reactions are instantaneous just as one brain would react. You see the same effects when shoals of fish scatter or form into defensive balls to defend themselves from predators. At will the individuals become one entity.
I think that crowds of humans can experience this as well; as players in an orchestra. Many musicians have explained that if the conditions are right, the music entrains them into something quite out of their own identity and they all become merged into the music as one. This indeed, for some, is the whole magical experience.