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Question # 1: Why is it that a flock of birds resting on a roof or beach, often take off -- all together; then fly around in a circle for often less than a minute, and then return to their original resting place -- and they do this repeatedly, often for a great portion of the day? Question # 2: What is the biological mechanism that makes possible large flocks of birds in flight, being able to wheel and otherwise maneuver in unison -- almost as though the entire flock were a single entity? Thank you in advance for your thoughtful attention.