A Dirty Jobs episode with Mike Rowe featured guys cleaning pigeon droppings. They were on apartment buildings and hospitals. Pigeons and their bugs can cause over 60 diseases in humans. The crew cleaned up the mess with detergents, pressure washers, scrub brushes and water. Then they'd do something to keep the pigeons away. The first one was tape that could be electrified to shock the birds if they landed on a ledge. It works like the electric cattle fences common in rural areas. Farm livestock learn in short order to stay away. Other methods are spikes, bird slides, repellant gel, and decoys.