I wonder sometimes if birds within flocks actually ‘know’ or recognize one another or if maybe I spend too much time wondering about such things. 
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Fun question. I programmed flock behavior for a game many years ago. (After a well known approch by a prof) 3 rules are necessary. Average velocity, direction and a min distance to 3-5 surrounding birds. For that the bird don't have to "know" the others. Just recognizing them 
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Interesting! Thx for your reply! Have also wondered how/why they don’t bump into each other when flying in flocks. I need to investigate to satisfy my curiosity.
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I am curious if they have ‘friends’ or family that they hang out with regularly. Inquiring minds.
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