Birds such as cliff swallows, barn swallows and the black-billed magpie build mud nests to lay their eggs. These birds combine mud pellets with grass, bark, hair or feathers to prepare nests. However, nesting swallows can become a nuisance, as they build mud nests around building exteriors, including eaves and porches. Swallows defecate and foul feed in and around their mud nests, staining and damaging exteriors of homes and other buildings. Use exclusion and other deterrent techniques as long-term preventive measures to stop swallows from building mud nests on your porch.
Fix monofilament fishing line on your porch to deter swallows from nesting. Use nails or screws to attach the lines about 12 inches apart across the entire length of your porch. Even though the monofilament is not a physical barrier, it seems to appear and disappear in the bird's line of vision, creating uncertainty and fear of a barrier and of possible entanglement.
Fix wire mesh or aluminum foil along the entire exterior wall of the porch to prevent swallows from nesting. The wire mesh acts like a barrier curtain to exclude swallows from entering your porch.
Create a slick surface to discourage swallows from nesting. Use slick waterproof paint to cover the walls of your porch. The painted surface is slippery and will not provide a firm base for the swallow to build its nest. You can also use masking tape to attach waxed paper to the walls of your porch to create a slick surface.
Fix metal spines, also known as porcupine quills, along the entire length of the exterior wall of your porch. You can purchase these four-inch long metal projections from commercial pest control companies.
Combine audio-visual scare devices such as ultrasonic bird repellents with visual scare devices like holographic balloons to scare swallows away from your porch.