Figure 4.

Typical trajectories in separate runs of the simulation of two birds with different preferred speed. Diverging straight lines: preferred routes; curved lines: paired flights. The preferred speed of bird 1 is , which is equivalent to the average speed in the experiments. The preferred speed of bird 2 is 19.72 m s⁻¹ in (a), 20.62 m s⁻¹ in (b) and 21.52 m s⁻¹ in (c). The faster bird can effectively lead the pair towards its preferred route. (Online version in colour.)