A freewheeling flock of birds is one of nature’s most endearing spectacles. The flock’s members move with uncanny coordination, changing direction in unison, splitting and reforming, and even landing as one. The intricacies of these synchronised flights are very difficult to entangle. Who is following whom? Is there even a leader and, if so, does the same bird always take up pole position? Our feeble eyes could never hope to discern the answers just by watching a flying flock. But fortunately, we have technology that can do the job for us.

Studying the collective movements of animal groups has been a difficult challenge. Many cameras can be used to film animals moving within the same block of space, but