Although rare, cowbirds have been documented parasitizing barn swallow nests, leaving a cowbird egg to be raised by the barn swallow.
Barn swallows have many predators including kestrels, hawks, owls, gulls, grackles, rats, squirrels, weasels, raccoons, bobcats, cats, snakes, bullfrogs, fish, and fire ants.
There are frequent cultural references to the barn swallow in literary and religious works due to its living in close proximity to humans and its annual migration.
The barn swallow is the national bird of Austria and Estonia.
Barn swallows drink water by skimming the surface of a body of water while flying.
Male and female barn swallows are similar in appearance, but males tend to be more vibrantly colored and have longer outer tail-streamers.
Introduced house sparrows are serious nest-site competitors with barn swallows and will take over nests and destroy eggs and nestlings.
There are no conservation measures for the barn swallow, but maintaining habitat, reducing pesticides, preserving wetland areas, long-term monitoring, research, and encouraging nesting can help preserve the species.
Female barn swallows select mates with symmetrical wings and tails and prefer longer tail feathers, all traits connected with increased strength, vitality, and longevity, as well as greater disease resistance.
Barn swallows have a symbiotic relationship with ospreys and will nest near them for protection while alerting the osprey of predators with alarm calls.
Barn swallows have an average lifespan of 4 years and those with longer, more symmetrical tails tend to live longer.
Un-mated male barn swallows often associate with a breeding pair for an entire season, helping with nest defense, nest building, incubation, and brooding, and may succeed in mating with the resident female.
The barn swallow is occasionally hunted for sport.
Both sexes of barn swallows help build the nest out of mud pellets, dry grass, straw, horsehair, and white feathers.
The main threat to barn swallows is agriculture including farming practices, loss of foraging areas, livestock rearing, improved hygiene, land drainage, and the use of herbicides and pesticides.
Barn swallows contribute to the ecosystem by eating an enormous amount of insects and controlling their populations.
Barn swallows forage opportunistically and will follow tractors and plows in order to catch the insects that are disturbed by the machinery.
Although all swallows are socially monogamous, barn swallows differ in the sharing of parental care, raising 2 broods a summer of 2-7 eggs each.
The barn swallow’s global population is estimated at about 290,000,000-500,000,000 individuals, 20% of which can be found in Europe.
Because barn swallow nests can be unsightly and can create cleanliness and health issues for humans, they are sometimes removed as a nuisance.
Barn swallows have a wide variety of calls used in different situations and will sing, both individually and as a group.
Barn swallows are aerial foraging insectivores and feed almost entirely on flying insects, such as flies, grasshoppers, crickets, dragonflies, beetles, and moths.
Because of its extremely large range and population size, the barn swallow is evaluated as “Least Concern” on the IUCN Red List of Threatened Species.
The barn swallow is migratory as it is susceptible to climate change and bad weather and will migrate to sub-Saharan Africa, southern Europe, South America, and South Asia in the winter months.
Barn swallows are socially monogamous, but genetically polygamous, as extra-pair copulations are common.
Barn swallows are often seen in large social groups and nest colonially, as a result of the distribution of high quality nests.
Barn swallows are very adaptable birds and nest anywhere with open areas for foraging, a water source, and a sheltered ledge, seeking out habitats of all types.
The barn swallow is the most widespread species of swallow in the world and is native in all the biogeographic regions except Australia and Antarctica.
In Anglophone Europe, the barn swallow is simply called the “swallow” and in Nothern Europe, it’s the only common species called a “swallow” rather than a “martin.”
Barn swallows are diurnal.
Six subspecies of the barn swallow are generally recognized.