Starling topological flocking · k nearest neighbors · collective motion
Topological flocking (Ballerini et al. 2008): unlike metric models (Vicsek), starlings align with their k=6-7 nearest neighbors regardless of distance. This makes the flock robust to perturbation — wave-like disturbances propagate at ~20 m/s. A predator causes a "void" that ripples through the flock.