(Columba livia var)
Feral Pigeons are more of a problem in large cities where the spaces provided by its buildings and human control of predators allows them to flourish. But they can be a pest in any urban environment. A small pigeon problem can quickly grow as they can breed throughout the year, thrive on the food that they find in abundance in any urban area and their natural tendency to roost on cliffs puts them at home on buildings.
One of the key problems caused by pigeons is fouling of buildings and pavements. Not only is pigeon mess incredibly nasty stuff (causes a range of reactions in humans) but it is also acidic, and can erode stonework and concrete.
Pigeons carry a range of infectious diseases which can infect humans, salmonella, tuberculosis and ornithosis (a mild form of psittacosis) to name a few.