when flying within a flock of birds, forward motion has a living rhythm to it. The heart of the flock surges forward this way, then that. No two birds are flying in precisely the same direction, but usually, everybody gets to the destination. Leadership flows from one bird to the next, not in order or for equal time periods, but rapidly, then slowly, then rapidly again, without thought or maps or schedules but rather with timing sensitive to the condition of the flock and its members, and considerate of the conditions of the locale, the time of day, the wind and weather.