Imagine a world where the only certain thing is the presence of pigeons. They are the ultimate expression of uncertainty, a constant reminder that even the most well-planned systems can be reduced to chaos by the whims of a few feathered fiends.
The Pigeon Paradox states that the more you try to control the pigeons, the more they will adapt and evolve, rendering your control measures ineffective. This is a classic case of the uncertainty principle in action, where the observer (in this case, the urban planner) is unable to fully predict the behavior of the system (the pigeons) without becoming an integral part of it.
It's a never-ending battle, really. You build a wall to keep them out, they find a way over, under, or through it. You install spikes to deter them, they learn to walk on the spikes. You put up a net to catch them, and they figure out how to fly around it.