Our previous work had shown that the attack behaviours of falcons are steered in a similar way to guided missiles, using a technique called proportional navigation. To understand how this works, imagine yourself as an aerial predator looking at your prey while closing in on it at speed. Your prey may try to evade you. But if you turn at a rate proportional to the rate at which the compass bearing of your prey changes, then you will take a path that gives you the best chance of intercepting your quarry.
For flock hunts the tactics differed
We used graphing software to trace how the line of sight drawn from the attacker to its target varied through the attack. This analysis revealed a clear answer: the direction of the line of sight to the target remained almost constant on all the attacks. It varied least on those that ended in a successful catch.
This geometry holds true for any pair of objects on a collision course. Mariners are taught to spot a constant bearing to avoid crashes with other boats and drivers use it intuitively to merge safely onto a busy road. The colony of up to 900,000 bats that we studied emerged en masse in the space of just a few minutes. For a predator plunging into this dense a swarm, there are so many targets at least one will be on a collision course. The difficult bit is to identify and catch it.
I thought this was super cool info. It may be old news to Steve since he is in raptor circles but it was new to me.
It wasn’t what I expected but I can see the logic of it.