Quick Answer
Barn swallows will live in birdhouses designed specifically for them. The entrance hole size, interior dimensions, location, and other factors must meet their needs for them to take up residence. With proper birdhouse design and placement, barn swallows can be enticed to nest in manufactured abodes.
Birdhouse Requirements For Barn Swallows
For barn swallows to occupy a birdhouse, some specific requirements must be met:
Entrance Hole Size
The entrance hole should be 2-2 1/2 inches in diameter. This allows barn swallows access while excluding larger species like starlings. A slightly oblong or oval hole can make it easier for the barn swallows to enter and exit.
Inside Dimensions
The interior floor space should measure at least 6 x 6 inches square and have a depth of 6 inches or more. This gives a pair of barn swallows enough room to build their mud nest and raise a brood. The box can be longer from front to back if desired.
Height Above Ground
Mount the birdhouse 12-20 feet high under the eaves of a building or other covered site. Barn swallows like to build their nests up high and prefer a location with overhead shelter.
Entrance Direction
Face the entrance hole toward an open area with a clear flight path. Barn swallows need maneuvering room to swoop directly into their nest. Avoid boxes with the hole facing a wall or obstruction.
Shelter From Weather
Barn swallows seek protected spots like barns or covered patios for nesting. Place the birdhouse in a covered location safeguarded from wind and rain which could damage the mud nest. Under eaves works well.
Predator Protection
Use a predator guard to prevent access to the nest by cats, raccoons, and other predators. A metal stovepipe or collar with a slippery interior surface mounted below the entrance hole can help deter climbers.
Nesting Shelves
Barn swallows attach their nest to the interior walls. Adding wooden shelves or cleats provides more surface area for adhesion. Nesting pairs will use 400-1400 mud pellets so sturdy anchorage is vital.
Materials
Construct the birdhouse from unfinished exterior-grade wood at least 3/4 inches thick to hold up over time. Avoid treated lumber which can contain harsh chemicals. Leaving the interior rough-sawn gives the nest a better grip.
Ventilation and Drainage
Barn swallows prefer a warm, dry nesting environment. Allow for air circulation and drainage by drilling a few 1/4 inch vent holes near the top. Small weep holes along the bottom let moisture escape.
Monitoring
Installing a side panel allows periodic inspection and cleaning between nesting attempts. Access aids proper maintenance and deters parasites. Attach the removable panel securely using machine bolts.
House Sparrows
House sparrows often compete for nest boxes. Installing the birdhouse in an open site away from buildings helps, as house sparrows prefer developed areas. Sparrow spookers also deter them from boxes suitable for barn swallows.
Nesting Timeframe
Get the birdhouse up 4-6 weeks before breeding season starts, as barn swallows need time to find and claim the nest site. In most areas breeding gets underway in April and May. Leaving the box up into summer gives time for multiple broods.
Why Barn Swallows Nest Where They Do
Barn swallows choose their nesting sites based on certain habitat preferences and requirements:
Cover
Barn swallows originally nested on cliff faces and in caves. Under eaves and other covered spots mimic the protected overhang of their ancestral breeding haunts. The shelter helps keep their mud nests intact.
Open Space
Unimpeded flight around the nest entrance is mandatory for these aerial acrobats. They need room to swoop directly in and out. Nesting on cliffsides provided this open access.
Elevation
Sites 6 feet above ground or higher offer enhanced safety from many predators. Higher vantage points also aid their insect pursuit. Elevated nests further ensure the fledglings have space to flap their wings.
Mud Source
Barn swallows gather hundreds of mud pellets to construct each new nest. Nearby water sources like ponds, streams, and puddles provide essential mud. Their nest architecture depends on this muddy building material.
Feeding Area
Productive feeding zones with healthy flying insect populations are a must. Barn swallows forage on the wing, consuming vast quantities. Their menu favors flies, mosquitoes, moths, beetles and other aerial arthropods.
Existing Structures
Rather than shaping nest burrows or drilling cavities, barn swallows modify their environment by affixing mud nest cups to substrates. Ledges, cliffs, cave walls, and manmade sites emulate the attachment points they seek.
Group Nesting
Barn swallows like to breed in loose colonies. Their mud constructions adhere readily to each other when in close proximity. Traditional nesting locales feature grouped placements which may aid social interactions.
Birdhouse Design Tips For Barn Swallows
Some additional pointers on designing and positioning birdhouses for barn swallows:
Durable Construction
Use weather-resistant wood at least 3/4 inches thick so the box remains sturdy and stable when placed under the eaves in exposed sites. Thicker wood also provides better insulation.
Sufficient Overhang
Mount the nest box where the overhang is 18 inches deep or more so rain and sun do not compromise the mud nest. Boxes placed under shallower overhangs usually go unused.
Open Front
An open fronted shelf style box works better than an enclosed box for barn swallows. They have more room to construct the nest how they wish without interior constraints.
Multiple Compartments
Including two or three compartments side-by-side allows for group nestings. Pairs using adjoining units often cooperate in feeding nestlings and defending sites.
Extend Nesting Season
In warmer areas, barn swallows may raise 3-4 broods. Leaving boxes up continuously gives them more opportunities to use the site for multiple clutches.
Active Sites
Prioritize placing boxes in areas already frequented by barn swallows if possible. Active feeding grounds, near existing nests, and known flight paths improve the odds of adoption.
Clear Flyways
Avoid points where structural projections, trees, or wires will impede the open flyways around the nest. Obstacles interrupt their aerial hunting and safe access to the site.
Gourd Houses
Natural gourds make attractive alternative nest sites. Hang drained sturdy gourds with proper entrance holes where barn swallows hunt and perch.
Siting Near Existing Nests
Look for potential sites on the same building or structure where barn swallows currently nest. Familiarity helps, and pairs may use both if space allows.
Mimic Eave Spacing
Mount boxes along the wall at intervals that match spacing barn swallows use on that structure naturally. Consistent placement encourages nest box use.
How To Attract Barn Swallows To Nest Boxes
It takes the right design and careful placement to convince barn swallows to take up residence in manmade nesting boxes:
Proper Dimensions
Follow barn swallow nest box plans exactly. The entrance size, internal space, depth, shelf width, and other measurements should match their requirements precisely or they will likely reject the box.
Ideal Location
Survey where barn swallows currently nest in the vicinity and mimic those site qualities. Reference factors like height, cover, orientation, nearby feeding, and flight paths.
Predator Protection
Deter predators from accessing the box with guards and collars. Preventing nest destruction is paramount. Monitor for signs of chewing, pecking, or claw marks and address if needed.
Preferred Materials
Rough-cut, natural wood matches traditional nesting substrates. Stay away from pressure-treated lumber and painted or stained wood which could introduce toxins.
Pre-Nesting Install
Make sure suitable boxes are up at sites well before breeding season when prospecting pairs are looking for nest spots. Early March is ideal timing in most regions.
Active Display
Running a barn swallow decoy on a wire near the nest entrance creates motion that grabs attention. Adjustable decoys allow perching, flying, and entry poses.
Clear Approaches
Barn swallows first focus on unimpeded access when evaluating nest sites. Prune encroaching branches, move obstructions, and open flyways around the box.
Mud Puddles
Ensure muddy puddles from irrigation, rain, or other sources are available within 100 feet to supply nest building materials. Provide mud if no natural wet spots exist.
Reduced Competition
Prevent starlings, house sparrows, and other aggressive species from taking over the box. Continuously monitor and control if needed until barn swallows accept the site.
Active Socialization
Be present when barn swallows investigate the box. Talking, gesturing, and going through motions of entering the box can help attract them during learning.
Are barn swallows territorial?
Barn swallows exhibit moderate territorial behavior:
- They defend their mud nest itself from intrusion by other barn swallows but allow neighbors to construct adjacent nests.
- They do not maintain distinct feeding territories but rather communally exploit flying insect populations.
- Nesting pairs may chase off conspecifics from very close range around the nesting site immediately prior to egg laying and when feeding nestlings.
- During nest building and after fledging, tolerance for proximity of other barn swallows increases.
- In migration and wintering grounds, barn swallows form enormous mixed flocks which indicates limited territorial needs outside of breeding context.
- Instead of occupying discrete territories, barn swallows nest in loose colonies where nests may be clustered densely together beneath a bridge or eave.
- Group nesting suggests benefits from maintaining social communities and cooperative relationships between pairs.
So in summary, the small areas immediately around active nests represent their primary defended spaces. Otherwise barn swallows are social, communal, and colonial in habits. Their use of open air hunting grounds negates formal territoriality.
Do barn swallows reuse nests?
Barn swallows demonstrate variable nest reuse behavior:
- Typically barn swallow pairs build a completely new nest each year even when using the same site again.
- They prefer to start fresh with new mud construction rather than refurbish the old nest.
- However, there are cases where they may reuse and add on to portions of an intact nest from the previous season.
- Renesting attempts after a failed clutch in the same season frequently involve repairing and relining the existing nest.
- Drought conditions that reduce mud availability sometimes lead to increased nest repairs versus new builds.
- Sudden cold snaps or storms early in nest building may also prompt reuse of surviving nest sections.
- Nest foundations and edges adhered to solid substrates have better odds of persisting through winter weather.
- Inconsistencies in nest reuse likely reflect climate effects, mud supply, damage levels, and energy tradeoffs.
In ideal conditions, barn swallows prefer construction of complete new nests each breeding attempt. But environmental factors and nest viability may lead to adaptive reuse in some cases.
How many broods do barn swallows have in a year?
The number of broods barn swallows produce in a single season varies by location:
Region | Broods Per Year |
---|---|
Southern Canada and Northern U.S. | 1-2 broods |
Mid and Southern U.S. | 2-3 broods |
Deep South and Southwest U.S. | 3-4 broods |
Southern Florida and Gulf Coast | 4-6 broods* |
*In warmer climates with extended breeding seasons, barn swallows may raise up to six broods. However, double brooding (two broods) is most common across their range. The likelihood of multiple broods depends on nesting success, food supply, weather, and length of the breeding period.
Do barn swallows migrate?
Barn swallows do migrate annually in most regions:
- Northern populations migrate south to warmer areas each fall.
- Migration begins in August and September and peaks from mid September to early October.
- They travel in flocks, feeding along the way and stopping periodically to rest and refuel.
- Barn swallows winter in the southern U.S., Mexico, Central America, the Caribbean, and northern South America.
- Return migration to the breeding grounds begins in late winter and early spring.
- Migratory barn swallows can travel 5000 miles or more each way over the course of a year.
- Some southern breeding populations may be resident year-round on territory while more northern birds migrate.
Tracking studies show connectivity between breeding populations in Alaska and Canada and wintering areas stretching from Panama to Argentina. The long distances traveled point to strong navigation abilities in barn swallows.
What do baby barn swallows eat?
Parent barn swallows feed their young primarily insects, especially flies:
- At first, parents regurgitate partially digested insects directly into the gaping mouths of chicks.
- As chicks grow larger, parents deliver intact captured insects directly to the nest.
- Flies, mosquitoes, moths, flying ants, beetles, grasshoppers, crickets, and other aerial insects are common food items.
- Barn swallows may catch dozens of insects per minute to satisfy the demanding appetites of fast-growing nestlings.
- Both parents share brooding and feeding responsibilities throughout the nesting period.
- Nestlings digest insects easily and get needed protein for growth and feather development.
- Crops of barn swallow nestlings often bulge visibly with the quantity of insects delivered by their parents.
The exclusive insect diet provides complete nutrition for young barn swallows. Parent birds work tirelessly to supply adequate food to fuel growth and prepare for fledging.
How do barn swallows build their nest?
Barn swallow nest construction is an intricate process:
- Nests begin with a foundation of coarse grass, feathers, and straw affixed to a vertical surface.
- Barn swallows gather mouthfuls of wet mud from nearby puddles and form it into pellets.
- Hundreds of these mud pellets are layered and shaped into a deep cup stuck to the base.
- The smooth interior cup is lined with fine grass, feathers, and sometimes hair for comfort.
- Construction happens in stages and both sexes participate in transporting and applying materials.
- Adjacent pairs contribute to each other’s nests resulting in clustered colonies.
- The complete nest is a marvel of avian engineering with sturdy mud walls and cod crafted shape.
- Nests are reuse rarely reused and most are rebuilt annually from scratch.
Meticulous nest construction using local natural materials is integral to barn swallow breeding success. Their adaptable mud cup designs are a direct result of needs shaped by aerial insectivore lifestyles.
Where do barn swallows nest?
Preferred barn swallow nesting locations include:
- Inside barns and other farm outbuildings.
- Under bridges and highway overpasses.
- On sheltered porches, garages, and patios.
- Along the eaves of houses and cabins.
- Under docks, piers, and wharfs.
- In boathouses, boat sheds, and marine structures.
- On cliff faces and rock outcroppings.
- In caves, crevices, and tunnels.
- On walls of dams, culverts, and drainage pipes.
Key features that attract nesting barn swallows are vertical surfaces for adhesive mud nest placement, cover from weather, heightened sites, and open areas for flight paths and foraging access.
How do you identify barn swallows?
Barn swallow identification tips:
- Blue-black iridescent upperparts and wings.
- Pale to rusty orange forehead, throat, breast, and belly.
- Deeply forked tail with long outer streamers.
- White spots on the tips of outer tail feathers.
- Buffy or reddish colored flank and vent region.
- Smaller size than other common swallows.
- More rounded wing shape than other swallows.
- Frequently observed flying low over fields catching insects.
- twittering social calls.
- Mud nest clusters under bridges and eaves.
In flight, the combination of forked tail, small size, coloring, and habitat use separate barn swallows from cliff, tree, bank, cave, and other swallow species with different nesting behaviors.
Barn Swallow Diet
The diet of barn swallows consists almost exclusively of insects caught during continuous flight:
- Flies are a preferred prey item and make up over 50% of stomach contents in studies.
- Mosquitoes, moths, beetles, grasshoppers, flying ants, bees, wasps, and mayflies are also commonly eaten.
- Barn swallows favor open or edge habitats where flying insects concentrate near water, woods, or structures.
- Fields, pastures, wetlands, rivers, lakes, and agricultural areas provide productive insect hunting grounds.
- Swallows may consume up to 850 insects daily during nesting season to satisfy energetic requirements.
- Efficient digestion of an insect diet gives barn swallows needed protein and calories.
- Aerial abilities and maneuverability allow grasping flying insects and drinking during sustained flight.
- Swallows roost together in reed beds at night where proximity may aid in communal foraging.
Specialization on catching insects on the wing is a key evolutionary adaptation enabling barn swallows to exploit an abundant niche as aerial insectivores.
Barn Swallow Nesting Habits
Notable barn swallow nesting behaviors include:
- Highly social and colonial, often with synchronized breeding.
- Nest placement undercover near open feeding areas.
- Mud nests affixed to vertical surfaces in clusters.
- Rapid nest construction using hundreds of mud pellets.
- Lining nests with soft grass and feathers.
- Multiple broods per season in warmer areas.
- Both sexes incubate eggs and brood young.
- Bi-parental care and feeding of nestlings.
- Nests typically not reused between breeding attempts.
- May change nest sites but often return to previous locations.
- Yearlings may help at nests of parents or neighbors.
The unique mud nest architecture, colonial habits, and dietary adaptations of barn swallows illustrate their specialized life history as aerial insectivores.
Threats and Conservation
Some key threats and conservation issues facing barn swallows today include:
- Declines due to reduced flying insect prey populations from pesticide use.
- Increased severe weather events and climate change disrupting breeding.
- Loss of nesting habitat like barns and bridges.
- Displacement by invasive bird species using nest sites.
- Mortality from vehicle collisions during migration and feeding.
- Negative impacts on mud supply from wetland drainage and drought.
- Nest destruction and disturbance from human activities.
- Contamination exposure from pesticides or other chemicals.
Protecting aerial insect abundance, breeding sites, clean water, and nesting areas will be important for the future security of barn swallow populations. Careful management around human structures can provide habitat.
Fun Facts About Barn Swallows
- Barn swallows are the most abundant and widely distributed swallow species worldwide.
- They can reach speeds of up to 35 mph in smooth level flight.
- Their migratory routes cover thousands of miles between nesting and wintering grounds.
- Barn swallows produce new clutch if eggs or young are lost, often renesting up to 4 times in a season.
- The male’s long tail streamers are attractive to females and increase mating success.
- Parents may kick slow-growing chicks out of the nest to increase survival odds of stronger siblings.
- Barn swallows roost communally in wetlands at night, sometimes numbering over 1 million birds.
- They sunbathe in groups by perching and fluffing up their feathers.
From their speed and agility to complex social behaviors, barn swallows display a wealth of fascinating adaptations for life on the wing.
Conclusion
With proper nest box design and placement that caters to their needs, barn swallows can successfully be enticed to adopt manmade abodes as substitutes for traditional muddy nesting structures. Their decline across much of their range means providing suitable artificial breeding sites could aid conservation. Understanding what attracts barn swallows to nest under eaves and bridges and replicating those qualities are the keys to encouraging usage of purpose-built nest boxes. With a specialized aerial insect diet, communal habits, and declining populations, increasing barn swallow nesting opportunities helps preserve these iconic birds and the ecosystem services they provide.