Others

The key ideas of the boiding algorithm are

1. Separation
2. Alignment
3. Cohesion

But these do not have to be the only motivators.

One could imagine that the boids prefer a certain heading over others, because it aligns them with a magnetic field.

Or boids prefer a certain location, because it offers a wide variety of food.

Whatever the back story, you are challenged to play with different kind of motivators and see how that changes the behavior of the boids.