Swallows building nests on houses is a common occurrence, especially in the spring and summer months when they are nesting and raising young. While having swallows nest on your house may seem charming, their mud nests can sometimes cause damage.
What kind of swallows build mud nests on houses?
There are three main species of swallows in North America that build nests on houses and other structures:
- Barn swallows
- Cliff swallows
- Eaves swallows
Of these, barn swallows are the most likely to build nests on residential homes. Cliff swallows tend to nest in large colonies on cliffs or under eaves of buildings, while eave swallows as the name suggests, build nests on eaves of buildings.
Where on houses do swallows build nests?
Swallows seeking to build nests on houses tend to choose these prime locations:
- Under eaves
- In porch corners
- On window sills
- Against beams or braces under decks
- In open sheds or garages
Any sheltered location that allows them to anchor their mud nest provides good nesting real estate for swallows.
When do swallows build nests on houses?
In most regions of North America, the peak breeding season for swallows is spring and early summer. Some key dates:
- Late March to April – Swallows return from migration and start scouting nest locations
- May – Nest building and egg laying
- June to July – Eggs hatch and nestlings are raised
- August – Young fledge and leave nest
Swallow nests on houses are most common in May, June and July when active nesting is taking place. Old nests may remain on houses into the winter.
What are swallow nests made of?
The mud nests built by barn swallows, cliff swallows and other species are made primarily of mud mixed with grass and straw. The birds collect mud in their beaks from puddles and moist soil, then carry it back to the nest location where they apply it in layers.
Swallow nests are formed into a cup shape and lined with soft grass, feathers or hair. The nest cup provides a cozy space for the eggs and chicks.
Barn swallow nests in particular feature a layer of mud built up under the nest, forming a shelf or ledge that helps support the nest. This mud ledge firmly anchors the nest in place.
Can swallow nests on houses cause damage?
Mud swallow nests become firmly adhered to the surfaces they are built on. When it’s time for the birds to migrate in the fall, the old nests are left behind.
Over time, accumulations of old swallow nests can cause some types of damage to houses, including:
- Blocking holes or gaps that allow water or insect access
- Trapping moisture against walls that can lead to peeling paint or rotting wood
- Weighing down surfaces like eaves
- Harboring insects or parasites in old nest material
In most cases however, a few swallow nests on a house cause no real harm. The potential for damage depends on the number of nests and their locations.
When are swallow nests a problem?
Homeowners may wish to remove swallow nests from their house if:
- Large number of nests accumulate in an area year after year
- Nests frequently become infested with bird mites
- Nests are blocking ventilation, weep holes or access points needed for maintenance
- Droppings are accumulating below nests and becoming a mess
- Nests trap moisture and cause rot or cosmetic damage
If swallow nests remain cleanly attached and are not causing any structural concerns or allowing pests, they can be left in place for the birds to reuse annually.
Can swallow nests on houses be prevented?
It can be challenging to exclude swallows once they have chosen a nest site, but measures can be taken to try to prevent them from attaching nests in undesirable areas.
- Install porcupine wire, coil springs or other prickly materials that deter birds from landing
- Hang mesh netting or sheets of plastic over areas swallows are attempting to nest
- Seal gaps and cavities swallows could potentially access
- Apply repellent gels on surfaces where they tend to build nests
Deterrents need to be applied early in nesting season before swallows establish sites and lay eggs.
When can old swallow nests be removed from a house?
To avoid disturbing active nests and potentially breaking the law, nest removal should only be done after breeding season has ended and nests are confirmed inactive. Some guidelines include:
- Avoid removing nests with eggs or baby birds still present
- Wait several weeks after young have fledged and left the nest before removing it
- In most areas, nest removal is safest between September – February when swallows have migrated south
- Always double check nests for any stragglers before removing
Note that covered nests that haven’t been used in awhile should still be avoided in spring, as swallows often rebuild and reuse the same nests year after year.
How can old swallow nests be safely removed?
Once nesting season is over and you’ve confirmed the nests are vacant, here are some tips for removal:
- Use a trowel, putty knife or similar tool to carefully pry and scrape the nest off the surface
- Soak hardened mud nests with water before removal to soften them up
- Wear protective clothing to avoid direct skin contact with old nests
- Seal gaps or holes left behind after nest removal
- Discard old nest material promptly and thoroughly clean the area
Take care when removing nests, as they often have sharp sticks incorporated into their structure which can scratch skin or puncture clothing.
Can removed swallow nests be reused?
Reusing an old swallow nest is not advised for a few reasons:
- Old nests may contain mites, fleas and other parasites
- Nests require repairs each season and deteriorate when exposed to weather
- Proper steaming and sterilization is difficult for mud nests
- New nests with fresh mud offer the most stable and sanitary housing
Rather than attempting to salvage them, it’s best to properly discard old nests and let the swallows build brand new ones next season.
Do you need a permit to remove swallow nests?
In the United States, swallows are protected under the Migratory Bird Treaty Act. This federal law prohibits harming or destroying active migratory bird nests without a permit.
However, the law does allow removal of old, inactive swallow nests, as long as no eggs or baby birds will be impacted. No permit is required in this case, as long as proper timing and care is followed.
It’s always a good idea to check your state and local regulations too. Some jurisdictions may have additional rules about old nest removal.
Will swallows rebuild nests after removal?
Even if you successfully remove old nests after breeding season, swallows often rebuild in the exact same spots when they return in spring.
To prevent this, deterrents need to be applied. Reflective tape, gels or netting can make previous nest sites less attractive options when the swallows come back.
Swallows strongly prefer their old nest locations and may rebuild up to 10 times if the site is not adequately blocked. Being vigilant and actively deterring them from the start of spring will help discourage nesting.
Do swallow nests on houses increase the risk of diseases?
A few health concerns related to swallow nests sometimes arise. However, the actual risk posed is minimal in most cases.
Histoplasmosis – This fungal infection is caused by breathing in spores that grow in accumulations of bird and bat droppings. Swallow nests do not generate the kind of large-scale droppings that significantly increase risk.
Avian flu – Wild birds can carry avian influenza viruses, but transmission to humans is extremely rare. There is no evidence swallow nesting increases flu risk.
Ectoparasites – Nest mites, swallow bugs and fleas may infest nests and bite humans if nests are directly handled. But they do not spread serious diseases.
Basic protective measures like gloves, masks and promptly disposing of old nest material will limit any potential health hazards.
Do swallows help control insect pests?
Swallows are highly effective aerial insectivores. A family of nesting swallows can consume thousands of flying insects per day at the height of breeding season.
Some key prey include:
- Flies
- Mosquitoes
- Moths
- Beetles
- Wasps
- Bees
- Aphids
Having swallows around helps naturally limit nuisance bugs in yards and gardens. Their voracious insect appetite makes them valuable to have nesting nearby.
Do swallows attack humans?
While fiercely protective of their nests, swallows do not act aggressively toward humans without provocation. Their small size means they pose no real physical threat.
However, swallows may make quick swooping flights near people that get too close to an active nest. This is meant to startle and drive off the perceived threat.
Actual contact is rare and any strikes are harmless. Maintaining a respectful distance from active nests will avoid provoking this defensive behavior.
How can you tell if a nest is active or inactive?
Determining whether or not a swallow nest still contains baby birds is important before removing it. Here are signs a nest is still active:
- Adult swallows flying to and from the nest
- High-pitched chirping sounds coming from the nest
- A nest cup that appears thickly lined and puffed up
- Fresh whitewash around the base
- Watching the nest to see if adults enter to feed
Signs a nest may be inactive:
- No swallows seen using it for 1-2 weeks
- Nest cup appears thin and flattened
- Lack of sounds when inspected up close
- No fresh whitewash below the nest
When in doubt, monitor the nest for adult and feeding behavior before removal.
Will keeping lights on at night deter swallow nesting?
There is little evidence that artificial night lighting has any effect on swallow nest site selection or building activity. Swallows readily nest on well-lit houses, barns and bridges.
In fact, outdoor lighting often attracts flying insects at night that in turn attracts swallows to productive feeding areas. Leaving lights on is unlikely to deter nesting.
What plants and flowers attract swallows?
While they do not rely on flower nectar like hummingbirds, attracting certain plants that draw insects can help lure swallows to your yard.
Good options include:
- Bee balm
- Coneflowers
- Lavender
- Zinnias
- Sunflowers
- Butterfly bush
- Dill and fennel
Landscapes with a mix of flowering annuals, herbs, native wildflowers and other insect friendly plants provide excellent swallow foraging habitat.
What are some fun facts about swallows?
- Barn swallows can fly up to 30 miles per hour.
- Cliff swallows build the most elaborate nests that resemble retort-shaped mud gourds plastered to surfaces.
- Swallows migrate astonishing distances, with barn swallows traveling up to 7,000 miles between their breeding and wintering grounds.
- The metallic blue feathers on the backs and wings of tree swallows result from microscopic air bubbles in their feathers.
- Parent swallows can make over a thousand feeding trips to bring insects back to their hungry nestlings in a day.
- Swallows are one of the most agile fliers, making tight aerial turns and dives to snatch insects mid-flight.
- Mud gathered by swallows for their nest can come from sources miles away from the nest site.
- Swallows have special feather adaptations that allow them to perch comfortably on vertical surfaces.
- Barn swallows readily reuse nests or build new ones right on top of old nests from previous years.
Conclusion
Swallow nests on or around a home can certainly cause some minor issues in certain cases. However, the insect-eating benefits these birds provide often outweigh their drawbacks.
Checking that nests are not actively in use, properly excluding swallows from problematic areas, and cleaning up old nests after breeding season are usually the best solutions for homeowners. Finding ways to coexist with these aerial acrobats allows both humans and swallows to happily share spaces together.
