Products that discourage pigeons are available to place on ledges. Place flexible mesh netting or rolled chicken wire on the ledge to create an unstable and uncomfortable surface on which to perch. The wire or netting can be fastened under eaves if this is the roost area. If access through open doorways such as loading docks is a problem, hand netting in loose panels that allow people to pass through but keep the birds out. Block openings to lofts and vents with netting, wire screen, metal or glass.
Pigeons prefer to roost on flat surfaces.
Install metal, wood, or some sheathing at a 60-degree or greater angle, to make it difficult for the birds to obtain secure footing. Despite its appearance, this product evidently does not harm birds. Use flexible mesh netting to protect trees and garden vegetables from droppings. Habitat modification can be effective. For example, thin tree branches where birds tend to gather.