Fegg

You can buy (or make) fake eggs. Feggs don’t fool pigeons and they don’t prevent egg-laying. The feggs just allow pigeons to have the pleasure of nest-building and egg-sitting (both of which they really enjoy) without hatching more pigeons, upsetting the pair’s relationship and/or harming the health of the laying female who will lay more too quickly if her real eggs are just removed without replacements.