Mud nests appearing on your house are almost certainly built by barn swallows or cliff swallows, two species that have adapted to nesting on human structures. These birds return to the same spots year after year, and their nests can create real headaches for homeowners, from stained walls to parasites that migrate indoors. Before you grab a scraper, though, there are legal protections you need to know about and a timeline that determines when you can act.
Which Swallow Built the Nest
Two species commonly attach mud nests to houses, and telling them apart is straightforward. Barn swallows build open, cup-shaped nests made of mud and grass, typically placed on a ledge or flat surface under an eave, porch, or garage ceiling. The nest looks like a half-bowl pressed against the wall, and you can see the eggs or chicks from below.
Cliff swallows build enclosed, bottle-shaped nests with a small round entrance hole. These nests hang under eaves and roof overhangs, often in tight clusters of dozens or even hundreds. If you see a gourd-like mud structure with a narrow opening, that’s a cliff swallow nest. Both species use mud as their primary building material, carrying it pellet by pellet from puddles and stream banks.
Why You Can’t Just Remove an Active Nest
Swallows are protected under the Migratory Bird Treaty Act of 1918, which makes it illegal to disturb the nest of any native bird without a permit. This means you cannot remove or relocate a nest that contains eggs or nestlings, even if it’s in an inconvenient spot or the droppings are piling up beneath it. Violations can carry fines.
The distinction that matters is active versus inactive. A nest with eggs, chicks, or an incubating adult is off-limits. An empty nest from a previous season, or one the birds haven’t started using yet, can be legally removed. This makes timing critical.
How Long Nests Stay Active
Barn swallows incubate their eggs for 12 to 17 days. After hatching, the chicks stay in the nest for another 15 to 27 days before fledging. So from the first egg to an empty nest, you’re looking at roughly four to six weeks per brood. Some pairs raise two broods in a single season, which can stretch the active window from late spring well into August.
Once the last chicks have fledged and the nest is confirmed empty, you’re free to remove it. Don’t wait until next spring. Swallows return to and reuse old nests, so leaving one up through winter is an open invitation for the same pair to come back.
The Mite Problem
Droppings and stained siding are the visible nuisance, but the less obvious issue is parasites. Bird mites, particularly the northern fowl mite and the chicken mite, thrive in swallow nests. In spring, nestlings can be parasitized by thousands of mites at once. While the birds are present, the mites stay on or near their host. The trouble starts when the chicks leave.
After fledging, mites left behind in the nest go searching for a new host, and that search can lead them indoors through gaps around eaves, vents, and window frames. Northern fowl mites can survive off a host for up to a month. Chicken mites are worse: they can persist for several months without feeding. Mites that make it inside are more of a nuisance than a health threat (they bite but can’t reproduce on humans), though the bites are irritating and can cause itchy welts.
Parasites can linger in old nests for up to three years after the birds leave, which is another reason to remove abandoned nests promptly rather than leaving them in place.
How to Safely Remove an Empty Nest
Wear gloves and a respirator mask, not just a dust mask, before handling any nest. Dried bird droppings can contain fungal spores, and as noted above, mites may still be present long after the birds are gone. A pressure washer is the most effective tool for removing the mud and cleaning the surface underneath. If you don’t have one, a garden hose on a high-pressure nozzle setting works, or you can use a long-handled scraper or putty knife.
After the nest is down, clean the area thoroughly. Scrub remaining residue with a disinfectant solution and hose it off. If you notice mites indoors after nest removal, vacuuming is the most effective immediate response. An over-the-counter aerosol insecticide labeled for mites can handle stragglers.
Preventing New Nests
Swallows are persistent builders. If you remove a nest without blocking the site, they’ll often start rebuilding within days. Prevention works best when you combine nest removal with physical barriers installed before nesting season begins in spring.
- Bird netting or wire mesh: Cover the areas where the wall meets the roof overhang, the most common nesting spot. Attach netting tightly so birds can’t squeeze behind it.
- Bird spikes: Install spikes along ledges and flat surfaces where cup nests would sit. These are less effective against cliff swallows, which attach nests to vertical surfaces.
- Vinyl strip curtains: For open entryways like carports or barn doors, overlapping vertical strips of vinyl plastic block access while still letting you walk through.
- Interrupting early construction: If you catch swallows in the first days of building, before any eggs are laid, knock the fresh mud down daily. Most pairs will give up on that location after several days of failed attempts.
The key is acting early. Once a nest is complete and eggs appear, you’re legally locked in for the duration of the nesting cycle.
The Upside of Swallows
Before you declare all-out war, it’s worth knowing what swallows do for your yard. A single barn swallow eats roughly 850 insects per day, or about 25,000 per month. Their diet is 99.8% insects, including mosquitoes, flies, beetles, and moths. A nesting pair feeding hungry chicks consumes even more. If the nest is on a shed or detached structure where droppings and mites aren’t a concern, leaving it in place gives you a highly effective, free pest control service all summer long.
For nests on your house itself, especially near doors, windows, or ventilation, the practical problems usually outweigh the benefits. But if you have a barn, outbuilding, or covered structure away from living spaces, redirecting swallows there (by leaving old nests or installing a small shelf as a nesting platform) lets you keep the insect control without the mess on your front porch.