Barn swallows are a familiar sight in rural areas, darting acrobatically through barns and around other structures. Their forked tails and colorful plumage make them easy to identify. Barn swallows migrate long distances, traveling between their breeding grounds in North America and their wintering grounds in South and Central America. These aerial acrobats put on dazzling flying displays while snatching insects in mid-air. But what makes barns and other structures so attractive to these birds?
Nesting Sites
Barn swallows are very selective when it comes to choosing a nest site. They prefer vertical surfaces that are protected from the elements. Barns, sheds, garages, under bridges and highway overpasses often fit the bill perfectly. Barn swallows build cup-shaped mud nests lined with grasses and feathers. They lay eggs and raise their young in these nests. Ideal nest sites provide protection from predators and poor weather conditions.
Barn swallows need an overhang or ledge to anchor their mud nests to. The vertical walls of barns and other buildings provide ideal surfaces for nest construction. Structures near open fields and bodies of water offer plenty of flying room for these aerial hunters to capture insects. Buildings also provide protection from predators that can access exposed cliff or canyon nest sites.
Nest Building
Barn swallows are unique among North American birds in their nest construction. They build cup-shaped nests out of mud they collect in their beaks from ponds or puddles. Hundreds or even thousands of trips may be required to complete a nest. Barn swallows mold the mud into a gourd shape with a tunnel-like entrance on top.
The nest starts with a mud platform anchored to the vertical surface. More mud is added to form the walls. The interior is lined with grasses and feathers for insulation. Nest construction can take 1-2 weeks, with both the male and female barn swallow contributing. Existing nests may be repaired and reused from year to year.
Ideal Nest Sites
For barn swallows, ideal nest sites share several common features:
- Vertical surface – allows the mud nest to be anchored to the surface
- Overhang – provides protection from rain and sun
- Sufficient height – 6 ft or higher provides protection from many predators
- Open areas nearby – needed for foraging on the wing
- Mud source – puddles or ponds nearby to collect nesting material
- Sheltered location – minimizes wind and disturbance
Barns rank very high on the scale of desirable barn swallow nest locations. The high, protected walls contain many potential nest sites. Nearby pastures and water sources provide foraging habitat. Other favored nest sites include the undersides of bridges, along cliffs, on highway overpasses, and under the eaves of buildings.
Roosting Sites
In addition to nesting, barn swallows also need overnight roosting sites. During the day, barn swallows may range up to a mile or more from the nest to forage. At night, they seek out sheltered places to roost communally. Again, barns provide many suitable spots.
Barn swallows prefer to roost in sites protected from wind and rain, and located high enough to avoid nocturnal predators. Favorite roosting spots include rafters, beams, window sills and door headers inside barns and sheds. Dense bushes or rows of shrubs are also used. Wherever they roost, barn swallows like to maintain proximity to their active nests.
Roost Requirements
Ideal roosting sites for barn swallows meet these criteria:
- Sheltered location – protected from severe weather
- Sufficient height – 8 ft or higher to avoid predators
- Flat surface – allows birds to sit and rest overnight
- Cover overhead – roof or overhang provides cover
- Near nest – roost is close to active nest site
- Good vantage point – open area above roost allows for quick takeoff
Like nest sites, barns often make very attractive roosting spots. The infrastructure of barns suits the ideal roosting conditions. Beams and platforms 6-20 ft up allow barn swallows to safely rest for the night. The enclosed but open nature of barns gives barn swallows what they need in a roosting site.
Food Availability
Access to plentiful food is another necessity for barn swallows. These small birds eat a diet consisting almost entirely of insects. Barn swallows are specially adapted to catch insects while flying. Their large gapes allow them to scoop up bugs while swooping through the air.
Barn swallows prefer open habitats near water when foraging. Fields, pastures, wetlands, rivers and lakes provide good hunting habitat. The presence of livestock and humans also increases insect numbers as more flies are attracted to manure and garbage.
Barns located in rural settings surrounded by farms, waterbodies and grazing lands serve the foraging needs of barn swallows well. There is likely no better place to find a dense swarm of flies and other flying insects than around a working barn.
Prime Foraging Areas
Barn swallows focus their foraging efforts in sites that offer:
- Open areas – pastures, fields, wetlands allow aerial pursuit
- Water nearby – habitats over water harbor more insects
- Livestock presence – attracts flies and other insects
- Structures – barns, stables and pens bring in insects
- Low vegetation – improves visibility and access
- Upland sites – ridges and hilltops where thermals form
The combination of open fields surrounded by barns and livestock pens creates prime barn swallow foraging habitat. Upland sites also allow barn swallows to utilize thermals and updrafts to gain speed and momentum during the chase.
Barn Swallow Migration
The presence of barn swallows in the United States and Canada is a seasonal phenomenon. Barn swallows winter in Central and South America, traveling incredible distances to reach their northern breeding territories each spring. Their migration is one of the longest among North American birds.
Some interesting facts about barn swallow migration:
- Total migration distance can be 4,000 – 8,000 miles each way
- Migrates solo, not in flocks like many birds
- Mainly follows coastlines and river valleys during migration
- Capable of 200+ mile flights non-stop over open water
- Travels at speeds averaging 20-25 mph
- Migrates both during daytime and nighttime
The swallow migration route generally follows coastlines, river valleys, and mountain ranges. Barn swallows migrate across the Gulf of Mexico, Atlantic Ocean, and Caribbean Sea. Peak migration occurs in April as birds hurry north to establish breeding territories.
Return to the Same Barns
Amazingly, individual barn swallows often return to the exact same nesting site year after year. If previous nest sites and surroundings offered what they needed, barn swallows will come back to the same barn. However, if conditions deteriorate due to urban development, renovations, or other habitat changes, site fidelity may weaken.
Barn swallows recognize suitable habitat and remember successful nest sites. Returning swallows get an earlier start on breeding. Arriving early allows them to claim the best nesting sites, attract a mate, and raise multiple broods. By coming back to a familiar barn, swallows gain big reproductive advantages.
Threats and Population Declines
Sadly, barn swallow populations have suffered major declines in recent decades. Habitat loss poses a worsening problem, especially the conversion of rural land and barns to urban development. Renovating barns by covering up or blocking potential nest sites also discourages swallows.
Pesticides reduce the insect prey base that barn swallows depend on. Climate change may be shifting swallow wintering grounds and migration patterns. Collision risks with vehicles and towers are increasing. Competition from introduced species affects nest sites.
Barn swallow numbers have dropped up to 75% in some regions. They are listed as endangered, threatened, or a species of special concern in many states. Supporting barn swallow populations requires conservation of their rural habitats and nesting structures.
How to Attract and Support Barn Swallows
Here are some tips to attract barn swallows and support their populations:
- Preserve old barns and sheds – repair and maintain existing structures
- Erect nest platforms – place boards or planks with overhangs
- Avoid renovating during nest season
- Leave existing mud nests intact when possible
- Avoid pesticide use – maintain natural insect populations
- Provide water source – pond, creek or fountain for mud gathering
Putting up nest cups, shelves or artificial nests may also be helpful. Maintaining healthy populations of barn swallows provides free insect control and the joy of watching these aerial acrobats flashing about. Their graceful flight and bubbly songs bring life to rural scenes.
Appreciating Barn Swallows
Watching barn swallows effortlessly gliding and swooping through the air as they chase down insects is a delight. Their streamlined, swept-back profiles and deeply forked tails equip them for speed and agility.
Barn swallows are also strikingly handsome birds. Their blue-black upperparts and cinnamon underparts make for a bold color contrast. The rusty orange face patch and throat set off the white forehead beautifully. Barn swallows have a variety of twittering, gurgling and warbling songs.
Beyond visual appeal, barn swallows play an important role in controlling flies and other insect pests. They are intimately associated with rural heritage and culture. Preserving barns and other classic swallow nesting sites is needed to maintain healthy populations of these special birds.
Key Facts
Here are some key facts about barn swallows:
- Small songbird – 5 to 7 inches length
- Pointed wings and deeply forked tail
- Blue-black upperparts, cinnamon underparts
- Makes mud cup nests on vertical surfaces
- Feeds exclusively on flying insects
- Migrates annually between North and South America
- Forms large communal roosts in fall
Technical species name: Hirundo rustica
Known for spectacular aerial displays while feeding. The sight of dozens of barn swallows swooping and diving together around barns is unmistakable and unforgettable.
Conclusion
Barn swallows and their mud nests on rural structures are an iconic symbol of the connection between birds and agriculture. As highly migratory insectivores, barn swallows need intact breeding areas and stopover sites along migration routes to maintain populations. They concentrate in habitats that provide nesting sites, roosting sites, food availability and other key requisites.
The declines in barn swallow numbers across North America over the past decades necessitate habitat conservation and protection efforts. Sustaining populations of barn swallows also involves public education and policy initiatives aimed at preserving rural and agricultural landscapes.
While challenges remain, the opportunity exists to stabilize and restore barn swallow populations. Each spring these birds embark on epic migrations in order to nest and forage in the habitats they evolved in. Supporting barn swallows pays tribute to the long association between their natural history and our own. The sight and sound of swallows gracing country skies is one we cannot take for granted. With thoughtful action, it’s a tradition that can continue.