system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are there pigeons everywhere?

Everywhere I go in the world that I've been to has had the same looking pigeons, why?
gpt
Pigeons are descended from rock doves.  They spread due to purposeful introduction and accidental. They are not native outside of Europe and Asia.   Pigeons are well adapted to cities as their natural habitat is rock faces on the oceans which building replicate.  Along with a lack of predators and abundant resources they have expanded populations along with humans. 




Pigeons increase the size of their clutch based on how well fed they are.

Since there's a ton of resources in cities for them they breed near the maximize, then reach an equilibrium as food runs scare.  Killing them doesn't eliminate the problem as the remaining pigeons will simply have more resources and breed faster. 

Removing the food sources is necessary to starve and shrink the population.