Swallows are graceful migratory birds classified as aerial insectivores, capturing their entire diet of insects while in flight. People attract these birds for two primary reasons: the pleasure of watching their acrobatic aerial displays and the significant benefit of natural pest control. A single Barn Swallow, for example, can consume an estimated 25,000 flying insects each month, including mosquitoes, flies, and aphids. Creating a welcoming environment involves a multi-step approach focusing on habitat, structure, and safety throughout the nesting season.
Creating the Essential Habitat
Swallows require a landscape that offers wide, unobstructed areas for foraging, as catching insects on the wing demands substantial open space. They commonly hunt over large fields, pastures, and water bodies, where flying insects are most abundant. The presence of water is also important for drinking; they often skim the surface of a pond or stream mid-flight to take a sip.
The availability of a consistent food source, consisting entirely of flying arthropods, is essential. Widespread application of insecticides severely reduces the insect populations that swallows rely on to feed their young, contributing to population declines of aerial insectivores. Maintaining a property free of broad-spectrum pesticides supports a healthy insect base for these birds.
Another fundamental requirement is the availability of soft, damp mud for nest construction, particularly for species like the Barn Swallow and Cliff Swallow. These birds create their nests by rolling mud into small pellets, which they cement together with grass and saliva. A single nest may contain over a thousand mud pellets, requiring a reliable source nearby.
If natural mud is scarce during the early spring nesting period, a temporary, accessible mud source can be created. Digging a shallow depression, roughly 3 to 5 feet in diameter, and keeping the soil wet with a garden hose will provide the necessary material. This mud source should be maintained throughout the nest-building phase, which often lasts one to two weeks.
Constructing Suitable Nesting Sites
Once the habitat is established, providing a specific physical structure for nest attachment is the next step. The type of structure depends on the species: Barn Swallows prefer platforms or ledges under an overhang, while Tree Swallows readily occupy nest boxes. Barn Swallows typically build their cup-shaped mud nests on a vertical wall or beam beneath a ceiling, such as in an open garage, shed, or under a porch eave.
To encourage Barn Swallows, install small wooden nesting platforms or ledges that mimic their preferred attachment sites. These platforms are most effective when mounted about 7 to 12 feet off the ground, mirroring their natural nesting height. The platform should be positioned with a small gap, ideally 2 to 3 inches, between the top of the nest site and the ceiling, allowing them to complete their mud cup.
The surface material is a consideration, as swallows struggle to adhere their mud nests to smooth surfaces like metal or finished wood. Using rough-sawn lumber or adding small protrusions, such as nails or staples, helps the initial mud pellets grip securely. Starter nest cups, which are pre-formed mud or plaster of Paris cups, can also be affixed to the platform to give the swallows a head start on construction.
Tree Swallows are cavity-nesters, best attracted by providing nest boxes mounted on poles in open areas. To minimize competition and predation risk, these boxes should be spaced at least 100 feet apart, as Tree Swallows are more territorial than colonial species. Locating the box well away from buildings, preferably 100 yards or more, significantly reduces the chance of takeover by the aggressive, non-native House Sparrow.
Protecting Swallows from Threats
Safeguarding swallow nests from both predators and competitors is necessary for a successful breeding season. Climbing predators, such as raccoons and snakes, pose a significant threat to nests accessible via a pole or wall. Installing a wide metal cone or stovepipe baffle on the support pole beneath the nest site prevents ground predators from reaching the eggs or young.
Domestic pets, especially cats, are a major source of predation; keeping them indoors or away from the nesting area during breeding months offers protection. For Tree Swallow nest boxes, the non-native House Sparrow presents a serious threat, often displacing or killing the native occupants. Non-lethal deterrents, such as a “Sparrow Spooker” (a device with mylar strips that flutter over the entrance), can be installed after incubation begins to frighten away competitors.
After the nesting season concludes, typically in late summer or fall, inspect and remove any old or unused nests. Removing old nests prevents the buildup of parasites, like swallow bugs and mites, that could infest returning birds the following year. This also prevents House Sparrows from claiming the site before the swallows return. Remember that all native swallows and their active nests are protected by the Migratory Bird Treaty Act. It is illegal to disturb or remove a nest once an egg has been laid or a bird is actively using the site.