Murmuration
Every bird watches only the few nearest it: keep apart, match their heading, drift towards their middle. Drag to fly round the flock, then send a hawk through it and watch the hole open and close.
Each bird adds up three steering directions over the neighbours it can see, and nothing else. The weight is how hard it pulls; the range is how far the bird looks for it. Nothing here mentions a flock, a shape, or where to go.
Matching is how well the average bird agrees with the birds around it: near one they are flying in step, near a third they are ignoring each other. Alignment asks the same question of the whole flock at once, and it sits lower, because a flock in the middle of a turn has birds pointing several ways while every one of them is still matching its neighbours. Clumping compares how unevenly the birds are packed against the same number thrown down at random, so one is chance and three is three times as uneven as chance.
Flight, weather and the roost
Turn rate is the one that changes the picture most, and it works the opposite way round to how it sounds. Birds that can turn instantly chase every twitch of their neighbours and the flock boils; birds that turn slowly cannot follow a wobble, so the whole flock is forced into one direction and flies as a sheet. The rolling dark bands are banked wings: a bird turning hard shows you its whole underside, and a bird flying level shows you an edge.
The roost is the point below the flock they keep coming back to, which is what stops the whole thing wandering out of frame. Wind pushes everyone the same way at once, so it moves the flock without changing its shape.