(Also something something Eristic Principle)
Starling murmurations fit the bill. The behavior of each participant can affect the whole flock such that there's a complex network of feedback loops involved. Their behavior, then, is not all that predictable.
Chaos by James Gleick is an entertaining book on the topic.
> “I’m interested in the transient moments when chaos briefly changes to order, and thousands of individual bodies appear to move as one,”
This quote in the article from the photographer makes it clear that she considered the birds to look/be chaotic before the brief moment when all the bodies moved as one.