Z googla:   Pigeons do not like strong spices, such as black pepper, chilli, or cinnamon. Make spice bags or spread a generous amount of these spices around popular pigeon nesting areas to keep them away.   Spices that you can try include cayenne pepper, black pepper, garlic, onion powder, chili powder and cumin. Any strong scented spice will do the trick. Pigeons hate water and you can use sprinklers and other motion activated water devices to scare the pigeons away.