Pigeons have a good sense of smell. They hate certain things. One of those things is cinnamon. Yes, you read that right. Sprinkle cinnamon where they perch. Your garden will smell like a cozy bakery. The pigeons will smell like defeat.
How To Keep Pigeons Off Vegetable Garden at Troy Haynes blog
Another trick: vinegar. Mix it with water in a spray bottle. Mist your fences and ledges. The smell is sharp. It lingers. The pigeons will think a lemon monster lives there. Let them think that.