If you haven't seen this, it's new to you so here it is.
Two friends out for a canoe ride get a front seat to one of nature's more spectacular phenomena: a massive group of starlings called a "murmuration".
Scientists aren't sure how flocking animals such as starlings and certain species of fish react in such amazing unison. As far as they can tell, the synchronization isn't based off a leader bird, but any individual's movement. Neighboring birds will take a cue, and the movement will ripple onward, creating the morphing shapes that grow and change in waves (rather than instantly across the flock). As for evolution's reason behind flocking behaviors, it comes down to strength in numbers: predators have a hard time focusing on an individual in a group of thousands.