Barn swallows, with their distinctive deep-forked tails and acrobatic flight, consume large numbers of flying insects, including mosquitoes and flies. However, their habit of constructing mud nests on human-made structures, particularly under eaves and on porches, creates significant nuisance due to droppings and noise. Property owners must implement effective and humane deterrence strategies that comply with federal wildlife protection laws. Preventing barn swallows from establishing a nest requires proactive intervention and a clear understanding of the legal boundaries surrounding migratory birds.
Legal Protections for Barn Swallows
Barn swallows are one of many species protected by the Migratory Bird Treaty Act (MBTA) of 1918, a federal law that makes it illegal to hunt, kill, capture, sell, or otherwise harm migratory birds. This protection extends to the birds themselves, their eggs, and their nests. The law strictly prohibits disturbing, destroying, or removing any nest that is “active,” meaning it contains eggs or young birds, or is currently being occupied by an adult swallow. The definition of an active nest is broad and includes nests where the adult bird is simply spending time, even if the construction is not yet complete. Violating the MBTA can result in substantial federal and state fines.
Structural Exclusion Methods
The most reliable long-term strategy for preventing barn swallows from nesting is structural exclusion, which physically blocks access to preferred nesting sites. Swallows favor sheltered, 90-degree corners, such as the junction between a vertical wall and an eave, to attach their mud nests. Installing physical barriers eliminates the possibility of nest attachment entirely, forcing the birds to relocate.
A highly effective method involves installing bird netting (3/4-inch to 1-inch mesh) mounted tautly at a 45-degree angle beneath the eaves. This creates a sloped surface where swallows cannot attach a nest. For ledges and I-beams, specialized products like smooth plastic or PVC panels, known as bird slopes, can be inverted under the overhang to create a slippery, angled surface. Overlapping vertical strips of vinyl plastic can also be hung in open entryways, creating a visual and physical barrier the birds will not fly through.
Environmental and Visual Deterrents
Modifying the texture of the nesting surface is a preventative measure that makes it impossible for the swallows’ mud pellets to adhere. Barn swallows cannot attach their nests to smooth surfaces, such as vinyl or aluminum siding, and the application of a slick coating or material can mimic this effect. Applying a smooth, hard-drying paint or covering the area with a smooth metal or plastic sheet removes the necessary rough texture required for nest construction.
Visual deterrents rely on reflections or the illusion of a predator to make the nesting area seem unsafe. Hanging reflective tape, holographic strips, or old CDs creates flashing light and movement that can confuse and frighten the birds. Decoy predators, such as plastic owls or hawks, are available, but their effectiveness is limited unless they are moved frequently to prevent the swallows from becoming accustomed to their stationary presence. Bird spikes, which are blunt, non-harmful wires, can also be installed on ledges and beams to eliminate perching spots and discourage the initial landing necessary for nest scouting.
Nest Removal Timing and Procedures
The only time a property owner can legally remove a barn swallow nest without a federal permit is when it is definitively inactive. An inactive nest is one that is completely empty, meaning it contains no eggs, no young, and is not being occupied by an adult bird. The ideal time for removal is either in the early spring, before the migratory swallows return to begin breeding, or late in the season after the birds have fully departed for the winter.
If swallows are attempting to build a new nest, the structure can be removed immediately, provided no bird has begun spending time in it. These mud constructions can be knocked down using a strong stream of water from a pressure washer or garden hose, or scraped off with a pole or specialized tool. When handling an old nest, it is advisable to wear protective gear, including gloves and a mask, as abandoned nests can harbor parasites and mites for up to three years. After removing the nest, the immediate installation of a permanent exclusion device, such as netting or a slope, is necessary to prevent the persistent birds from rebuilding in the exact same location.