Barn swallows are protected under federal law, so the most effective deterrent strategy is prevention before nesting begins. Once a barn swallow starts spending time in a nest, even an incomplete one, removing it is a federal crime under the Migratory Bird Treaty Act of 1918. That means timing matters as much as method. The best window for installing deterrents is late winter or early spring, before swallows return to your area.
Why You Can’t Just Remove a Nest
The Migratory Bird Treaty Act makes it illegal to hunt, kill, capture, sell, or otherwise harm migratory birds, and that protection extends to nests in use. “In use” has a broader definition than you might expect. A nest doesn’t need eggs or chicks inside it. If a bird has begun spending time at the site and constructing with mud, that nest is legally protected until it’s empty again. Trapping or shooting the birds is also illegal.
If barn swallows are causing documented damage to a structure, you can apply for a federal Migratory Bird Depredation Permit through the U.S. Fish and Wildlife Service. The process starts by contacting USDA Wildlife Services for an evaluation. A biologist assesses the situation and, if lethal or disruptive action is warranted, issues a recommendation form (WS Form 37) that you submit alongside a permit application and fee. These permits specify the species, methods, number of birds, exact locations, and dates. This route exists for serious damage situations, not general nuisance complaints, and the process takes time.
Netting: The Most Reliable Physical Barrier
Exclusion netting is widely recommended by extension services as the most effective way to keep barn swallows from nesting on porches, eaves, and overhangs. The idea is simple: hang a curtain of netting from the outer edge of the eave down to the wall of the building, blocking access to the sheltered surfaces where swallows attach their mud nests.
Use plastic bird netting or poultry wire with a mesh size of about 3/4 inch. One-inch mesh has also been used successfully, though smaller gaps reduce the chance a bird could slip through. The netting should be pulled taut so it doesn’t flap in the wind, which causes tangles, breakage at mounting points, and an unsightly appearance. Never use mist nets or any thin, flexible netting with loose pockets or wrinkles. These can trap and entangle swallows, which defeats the purpose and could violate federal protections.
For best results, install netting before swallows arrive in your area. You can leave it up year-round or take it down after nesting season ends. Permanent installation saves you the yearly task of re-mounting but does change the look of your building.
Bird Spikes and Structural Modifications
Bird spike strips, sold at most hardware stores, can be mounted along ledges, beams, and the junction where walls meet eaves. These work by eliminating the flat, stable surface barn swallows need to anchor their mud nests. Spikes are a good option for narrow ledges and structural beams inside barns, carports, or covered patios where netting would be impractical.
Smooth, slick surfaces also help. Barn swallow nests are made of mud pellets, and mud doesn’t grip well on non-porous materials. Covering a favored nesting spot with smooth plastic sheeting or a slick board can prevent nests from adhering. The key is eliminating texture. Rough wood, concrete, and stucco give mud something to grab onto. Smooth plastic, metal, or painted surfaces don’t.
Visual and Sound Deterrents
Visual deterrents like fake owls, predator eye balloons, and coyote decoys can discourage barn swallows for a short time. The catch is that swallows are intelligent birds and habituate quickly. If that plastic owl sits in the same spot for a week, swallows will figure out it’s harmless. Moving decoys to new positions every few days extends their usefulness, but most experts consider visual deterrents a supplement to physical barriers rather than a standalone solution.
Sound machines that broadcast predator calls or ultrasonic frequencies can also push barn swallows away from a specific area. Predator cry machines mimic the sounds of hawks and other raptors, while ultrasonic devices emit high-frequency tones that birds find unpleasant. These work better in semi-enclosed spaces like barns or garages than in open outdoor areas where sound disperses. Like visual decoys, sound deterrents lose effectiveness over time if used in the same pattern. Alternating between different sounds and combining them with physical barriers gives better results than relying on noise alone.
Why Sticky Gel Repellents Are a Bad Idea
Gel-based bird repellents are marketed as a humane deterrent, but the reality is far less clean. These sticky substances are non-selective, meaning any bird that lands on them gets stuck. Reports from wildlife rehabilitation centers describe birds with gel coating their feet, beaks, and feathers. The substance collects dirt and debris, creating flight problems and making it impossible for birds to eat. One rehabilitation center in South Africa documented 78 cases of gel-affected birds over five years, with cleanup taking days to weeks per bird. Many affected birds die of starvation.
Beyond the animal welfare concerns, trapping a protected migratory bird in a sticky substance could be considered “take” under the Migratory Bird Treaty Act, exposing you to legal liability. Physical exclusion methods like netting and spikes accomplish the same goal without these risks.
Timing Your Deterrent Strategy
Barn swallows return to the same nesting sites year after year. If you had nests last season, expect the birds back. In most of the United States, swallows begin arriving in March and April, with nesting activity peaking from April through July. Your preparation window is late winter, before the first scouts show up.
Start by removing old, empty nests from the previous season. Empty nests outside of breeding season are not protected, and removing them eliminates the ready-made foundation that returning swallows look for. Then install your barriers. Netting over eaves, spikes on beams, smooth coverings over favored spots. Add visual or sound deterrents as a secondary layer if you’re dealing with a persistent colony.
If you missed the window and swallows are already nesting, you’ll need to wait until the birds and their young have left before making changes. Barn swallows typically raise one to two broods per season, so an active nest site may not be vacated until late summer. Once the last brood fledges and the nest is truly empty, you can legally remove it and install deterrents for the following year.