How can I prevent sparrows from roosting in my yard?
You might just leave them alone, unless they are creating an unhealthy mess or destroying things. If you must control them, you can try applying a sticky repellent of some sort (polyethylene, resin, or castor oil) to the surfaces on which they perch. You can find these repellents in aerosol, tube, or spray form at a gardening or hardware store. You’ll have to treat all surfaces for this method to be effective. Some folks try keeping birds away with sound or stuffed animals, but these rarely work with sparrows. Don’t create further roosting problems by adding any ornamental masonry, wood, or metal containing small holes in which sparrows can nest. Any openings should be large and airy to discourage nesting. If you have small openings around, plug them with an appropriate material, such as wood, hardware cloth, screening, or metal.