How to Keep Birds Out of a Barn or Open Outbuilding

Sparrows and starlings in a barn mean fouled feed, blocked vents and fire risk. Exclusion at the openings, timing around nesting, and what to do about feed.

By Salma October 23, 2026 4 min read Save to Pinterest

Three sparrows perched along the ridge of a corrugated outbuilding roof against a clear sky — Photo: sergei_spas, Pixabay Content License, via Pixabay

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A barn is shelter, warmth and spilled grain under one roof. That is why scarers fail inside one and why the whole job is exclusion plus feed discipline.

The short answer

Keeping birds out of a barn is exclusion work, not deterrence: scarers cannot compete with shelter and spilled feed. Net the large openings with knotted netting under three-quarter-inch mesh on a tensioned cable, screen every vent and gable gap with half-inch hardware cloth, close the eaves and roof-to-wall gaps, and move all feed into lidded bins. Do the work in late autumn or winter — active nests are protected almost everywhere, and a mid-season exclusion seals chicks in. Barn swallows are protected and eat insects; the target here is starlings, sparrows and pigeons in numbers.

Exclusion, not scarers. A barn beats any deterrent
Mesh 3/4 in or smaller, or sparrows walk through
Lidded feed bins matter as much as the netting
Late autumn or winter, never mid-nesting
Leave the swallows. Protected, and they eat flies

Why it is worth doing

Fouled feed and water — droppings in a trough spread salmonella and campylobacter through a herd or flock
Blocked ventilation. Nests packed into ridge vents and ducts are a common cause of a barn that will not clear its own humidity
Fire risk. Nest material built against wiring and into light fittings is dry, loose and sitting on a heat source
Respiratory risk from years of dry droppings in a closed loft
Structural mess — droppings corrode galvanised sheet and rot timber over time

Timing, and the law

Active nests are protected in the UK, the EU and most of the world
In the United States, the Migratory Bird Treaty Act covers most species — but house sparrows, European starlings and feral pigeons are introduced and are not protected under it. Those three are the usual barn problem
Barn swallows are protected in North America and Europe both. Do not exclude them

Do the work in late autumn or winter. Even where removal is legal, exclusion during nesting seals chicks inside the building, which is both inhumane and a smell problem for months.

Clear the loft before you close it

A barn loft with years of accumulated dry droppings is the one genuine health hazard in this job. Disturbed dry droppings release fungal spores, including Histoplasma.

Dampen first with a mist, bag rather than sweep, ventilate, and wear an N95 respirator. For a large accumulation in an enclosed space, this is a contractor’s job.

Close the building, opening by opening

What goes over each kind of opening

Opening	Fix	Mesh
Large doorway or bay	Knotted netting on tensioned cable	Under 3/4 in
Ridge and soffit vents	Hardware cloth, screwed to battens	1/2 in
Gable gap	Hardware cloth or sheet infill	1/2 in
Eaves and roof-to-wall gap	Foam-filler strip or mesh	1/2 in
Broken window	Glaze or board, not net	—
Light fittings and voids	Cap or cone them off	—

Walk the building at dusk and watch where birds enter. Mark every point. There will be more than you expect, and the small ones matter most
Screen the vents and gable gaps first. Half-inch hardware cloth, screwed to battens, not stapled on. Sparrows will peck at stapled window screen until it gives
Close the eaves line. The roof-to-wall junction on a steel building is the single most common sparrow entry, and the profile filler strips made for it solve it
Net the big openings. Knotted netting hung on a stainless cable with turnbuckles, drawn taut, hog-ringed along the edges. Not draped — slack netting tangles birds and tears
Leave the working doors workable. A net on a curtain track or a weighted strip curtain on the main bay beats a net you cut a hole in within a week
Walk the inside at dusk again a week later and find what you missed

Remove the reason they came in

Exclusion holds far better when the building is not worth the effort of breaking into.

Feed in lidded bins. Metal, with a latching lid. This is the single biggest change
Sweep spills daily. A concrete apron and a broom are cheaper than netting
Cover troughs or site them where droppings cannot land in them
Clear nest material from the rafters, lights and ducts once the season is over, and cap the voids so it is not rebuilt in the same slots
Clean up around the grain bins outside too — an outdoor feeding ground keeps a flock on site waiting for a gap

Perch strips on the rafters, where netting cannot reach

Some barns have an open roof structure that cannot practically be netted. Anti-perch strips bonded along the top of the main rafter runs take away the roosting surface in the places that collect the most droppings.

It is a partial fix, and partial is sometimes all a working building allows. Target the runs directly above feed, water and stalls.

What does not work in a barn

Ultrasonic repellers. Birds do not hear in that range
Reflective tape and spinners indoors. Habituated in days, because the shelter is worth it
Decoy owls and hawks. Perches, within a week
Poison and lethal control. Illegal for protected species, and it leaves dead birds in the structure. It also does nothing about the opening that let them in
A net with a hole in it. One gap and the flock finds it the same evening

Common questions

How do I keep birds out of my barn?

Exclusion at the openings, and removing the reason they are inside. Net the large openings with knotted netting on a tensioned cable, screen every vent and gable gap with hardware cloth, close the gaps at the eaves and the roof-to-wall junction, and get all feed into lidded bins. Scarers inside a barn barely work, because the building offers shelter and food that no amount of flashing tape outweighs.

What size mesh keeps sparrows out?

Three quarters of an inch or smaller. Sparrows push through an inch, and anything above that excludes pigeons only. For vents and small gaps, half-inch hardware cloth is the standard, because it is rigid enough to resist pecking and small enough to stop a sparrow. Netting should be knotted rather than extruded, which sags and tangles.

When can I remove birds from a barn?

Outside the nesting season, and only once the nests are genuinely empty. Active nests are protected by law in most countries, and in the United States the Migratory Bird Treaty Act covers most species, although house sparrows, European starlings and feral pigeons are introduced species not covered by it in the US. Even where removal is legal, a mid-season exclusion leaves chicks sealed in. Late autumn and winter are the right windows.

Are birds in a barn actually a problem?

Several real ones. Droppings foul feed and water and spread salmonella and campylobacter among livestock, nests in rafters and ducts block ventilation, nests packed into light fittings and against wiring are a genuine fire risk, and accumulated dry droppings in a closed loft carry fungal spores. A pair of barn swallows is a different matter from a hundred starlings — and swallows are protected, and eat insects.

Should I keep barn swallows out?

Usually not. Barn swallows are protected across North America and Europe, they eat enormous numbers of flying insects, and a few nests are a small price for that. If a nest sits directly above a feed bin or a stall, fix the local problem with a shelf or a board beneath it rather than excluding the birds. The exclusion advice here is aimed at starlings, sparrows and pigeons in numbers.

Do ultrasonic bird repellers work in barns?

No. Birds hear poorly in the ultrasonic range, and the devices are sold on an assumption that does not hold. Audible distress-call units do have some effect outdoors but are impractical inside a working building and lose effect as the flock habituates. In a barn the money belongs in netting and hardware cloth, which keep working with no batteries and no habituation.

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