An uncontrolled pigeon population can be both a nuisance and a health risk. Pigeons are unwelcome for everything from their messy droppings to concerns about the diseases they carry. While they may be somewhat difficult to control, there are several methods that can help keep them from overpopulating one area.
Create a physical barrier to discourage roosting. Use screening or bird netting to block off areas like the eaves of your house, where pigeons tend to gather.
Place "bird strips" (strips of metal that that contain upward-pointing spikes at various angles) in places like the tops of fences and edges of the roof. The metal spikes will prevent pigeons from having a comfortable place to land.
Use chemicals to take care of the problem. These are available in two forms---pigeon repellent and pigeon poison. While poison may help take care of the problem more permanently, it leaves the property owner with the unpleasant question of how to deal with the abundance of dead pigeons once the poison has taken effect. Perhaps the better solution is to use a chemical repellent such as Bird-X. A product called Avitrol creates an interesting compromise between poison and repellent. When ingested, Avitrol causes pigeons to behave in a way that scares away the rest of the flock. Although the original pigeons die, the rest of the flock leaves before any more are poisoned.
Put up a scarecrow. While it may sound old-fashioned, this tried and true method has been around so long for a reason. You may also want to make or purchase artificial animals that will scare pigeons away, such as owls and snakes.
Steer away from ultrasonic repellent devices. These are not effective in deterring pigeons.