Barn swallows nest inside human-made structures, building mud cups attached to vertical walls or beams, typically returning to the same site each spring. They are not cavity nesters; they require an open, sheltered surface with a rough texture for their mud nests to adhere to.
Nest Appearance and Construction
A barn swallow nest is an open cup, not a closed dome like an ovenbird’s. The male and female collect mud in their bills, mixing it with grass and sometimes feathers, then lay it down in layers. Over about a week, they build a cup that is roughly 4-5 inches wide and 3 inches deep. The inside is lined with fine grass and feathers. The mud is the key structural material; if the weather is too dry or too wet, construction pauses.
Where Barn Swallows Nest
As their name suggests, barn swallows strongly prefer agricultural buildings. They choose sites with:
- An open entrance (like a barn door or broken window) for easy swooping access.
- A rough, porous surface for mud adhesion—wood, concrete, or stone are common.
- Protection from rain and direct sun, often under eaves or on a beam.
- Nearby open fields or water for insect hunting.
They will also use garages, sheds, under bridges, and even porch ceilings. Unlike cliff swallows, they do not build enclosed gourd-shaped nests.
Nesting Season and Clutch Size
In North America, barn swallows arrive from wintering grounds in South America in March or April. Nest building begins soon after, with the first eggs laid by May. A typical clutch is 3-5 white eggs with brown speckles. The female incubates for about 12-17 days. Chicks fledge about 18-23 days after hatching. Many pairs raise two broods per season, especially in the southern parts of their range. They often reuse and repair an old nest for the second brood or the following year.
Behavior Around the Nest
Both parents feed the chicks, making hundreds of trips per day to catch flying insects. Barn swallows are highly territorial around the immediate nest but may nest in loose colonies if space allows. They are also known for their sharp, twittering calls and swift, acrobatic flight. When a predator approaches, they will mob it, diving and calling loudly. They do not generally attack humans but may swoop close if a person lingers near the nest.
Common Problems and Misconceptions
A frequent misconception is that barn swallows carry diseases that make them dangerous to humans. In reality, they are not significant disease vectors, though their droppings can accumulate and create a sanitation issue. Another problem is nest collapse: if the mud was built on a smooth surface or during dry weather, it can fall, sometimes with eggs or chicks inside. People also worry that disturbing a nest will cause abandonment—this is only true if the adults are scared away for a long period; brief checks are usually tolerated.
How to Help or Manage Barn Swallow Nests
If you want to encourage nesting, provide a rough wooden shelf or a rough-textured beam in a sheltered spot. If you need to prevent nesting, block access before they arrive in spring—once they have eggs, it is often illegal to disturb them under the Migratory Bird Treaty Act in the U.S. If a nest falls, you can place the chicks in a small basket or container and attach it near the original site; the parents will usually find them. For droppings, place a board or tray below the nest to catch waste.
Differences from Other Swallows
Barn swallows are often confused with cliff swallows or tree swallows. Cliff swallows build enclosed gourd-shaped mud nests in dense colonies, usually under bridges or on the outside of buildings. Tree swallows nest in cavities (birdhouses or dead trees) and have white underparts, not the rusty orange of barn swallows. Barn swallows have a deeply forked tail and a blue-black back, which is unique among North American swallows.
Frequently Asked Questions
How long do barn swallow babies stay in the nest? Chicks remain in the nest for about 18-23 days after hatching. After fledging, they stay near the parents for another week or two as they learn to catch insects.
Do barn swallows use the same nest every year? Yes, they often return to the same nesting site and may reuse and repair the same mud nest for several years. They add fresh mud and new lining each season.
Is it safe to remove a barn swallow nest? In the U.S., barn swallows are protected under the Migratory Bird Treaty Act, so it is illegal to remove an active nest with eggs or chicks. Inactive nests can be removed in the fall or winter, but be aware they may rebuild.
What should I do if a barn swallow nest falls down? If the eggs or chicks survive, place them in a small open container (like a margarine tub) with grass and attach it as close to the original spot as possible. The parents will usually continue to care for them.
Why do barn swallows build nests on my house? They choose homes with overhanging eaves, rough siding, and easy access to open areas for hunting. The location offers protection from rain and predators, and the mud adheres well to wood or stucco.
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