Out My Backdoor: Barn Swallows Offer Unique Window into Nesting

A young barn swallow preparing to fledge
A young barn swallow preparing to fledge (Terry Johnson)


By Terry W. Johnson

Each year countless birds nest close to our homes. In Georgia, at least a dozen or more species of birds nest in our backyards. However, none offer a better chance to watch their nesting behavior than the barn swallow, especially when they nest on the side of a house or nearby outbuilding.

The barn swallow has the distinction of having the most expansive breeding range of any other swallow. That range stretches across much of North America, Europe and Asia. Depending on where swallows breed, they winter in Australia, South America or Africa.

Europeans often refer to the barn swallow as simply “the swallow.” Thomas Jefferson called it the American swallow.

Over the centuries, barn swallows have become very popular. For example, barn swallow is the national bird of both Austria and Estonia. In many cultures, when a barn swallow builds a nest on a barn it is considered good luck. In Estonia, legend has it that anyone who commits the crime of killing a barn swallow with go blind.

A Native American legend offers a fanciful explanation as to why the barn swallow has a forked tail. Supposedly, one day a barn swallow had the audacity to swipe fire from the gods. The bird then gave fire to humans. In an effort to thwart this thievery, the gods shot flaming arrows at the bird. One hit the swallow at the base of its tail, burning away the central tail feathers. Ever since, the barn swallow has had two long outer-tail feathers separated by a wide space.

With such an expansive breeding range, over countless generations the barn swallow has developed an affinity for living close to humans. This has undoubtedly enabled the barn swallow population to grow as civilization swept across much of the globe. Whereas the bird originally nested in places such as caves and cliffs, barn swallows began nesting on and in manmade structures such as sheds, barns, stables, bridges, docks, culverts and, well, you name it. In eastern North America, the swallow's propensity for nesting on such structures is so strong that barn swallow nests are rarely found elsewhere.

In North America, historians believe barn swallows probably even nested on structures fashioned by Native Americans. When European colonists arrived in the New World, barn swallows quickly took advantages of buildings built by colonists. Peter Kalm, a Swedish naturalist who visited what is now known as the northeastern U.S.  during the mid-1700s, wrote that barn swallows nested both inside and on the outside of the colonists' homes.

Barn swallows have been documented nesting is some odd places such as a wrecked tanker marooned along the Massachusetts coast, in a kerosene lantern, in cellars, close by a blacksmith's forge and even on a train.

If barn swallows nests on your home or outbuilding, you will have an unobstructed view of the birds' entire nesting effort, from building the nest through fledging the young. If you watch the swallows' nesting habits, the following description of the process will help understand what you are seeing.

Both the male and female swallows take part in selecting the nest site and construction, incubating the eggs, and feeding the young.

Each year, about 44 percent of all barn swallows will return to nest in the same area they nested the previous year. If the birds decide to renovate their old nest, they begin by throwing out and replacing old nesting material and adding more mud around the nest's rim.

If the birds build a new nest, they will spend one to five days plastering a mud disk to the wall or other vertical surface where the nest will sit. This involves using their bills to collect pellets of sticky mud, mixing it with saliva and pieces of grass, straw, pine needles and even fishing line, and then attaching that material to the structure that will support the nest.

Once the base is in place, the birds work from three to 15 days fashioning a mud cup. If you closely examine the nest, you can actually see the outlines of the individual mud pellets that were used.

The adults will then tackle lining the nest with a variety of materials such as hair (horse, human, etc.), feathers, cotton, moss, rootlets and fine grass. For some reason, the female often spends more time lining the nest than the male. This part of the process can take one to five days.

In all, building a nest will require 1,300 or more trips by a pair of barn swallows, a truly monumental task.

Once the nest is completed, the female spends three to seven days laying a clutch of three to seven white to pinkish eggs decorated with brown, lavender or gray spots. For the next 12 to 17 days, the pair will incubate the small, fragile eggs.

When the eggs hatch, the adults will feed their rapidly growing young for 15 to 27 days, until they are ready to fledge. But that doesn’t mean the parents’ work is over. Barn swallows often nest twice a year.  It should be noted that sometimes young swallows from the year’s first brood will help their parents feed the second brood.

While it might seem that nesting on or near our homes would offer protection to the eggs and young, that’s not always the case. For barn swallows, nesting is actually fraught with danger.

House sparrows will pilfer the swallows nesting material. (Not to be outdone, barn swallows will steal nesting material from one another.) House sparrows will also often puncture or even toss out the swallows' eggs and young. Barn swallow eggs are also targeted for piercing by starlings, and even eastern phoebes will steal eggs from barn swallow nests.

If that isn't enough, male barn swallows that don’t have mates will occasionally kill the young swallows.  It is believed this is done to enable the perpetrator to eventually mate with the female that produced the young.

Birds are not the only predators, of course. Eggs and young are sometimes eaten by gray rat snakes, house cats and raccoons.

While the trials of barn swallow are not unique to them, the fact that these activities take place in plain sight—not in a nest box, treetop or deep within a shrub—provides a front row seat to a true wildlife drama. If you have a barn swallow nest nearby and take the time to observe them, chances are you will gain a greater appreciation of these birds and the effort it takes for them to fledge their young.

Terry W. Johnson is a former Nongame program manager with the Wildlife Resources Division and executive director of The Environmental Resources Network, or TERN, friends group of the division’s Nongame Conservation Section. (Permission is required to reprint this column.) Learn more about TERN, see previous “Out My Backdoor” columns, read Terry’s Backyard Wildlife Connection blog and check out his latest book, “A Journey of Discovery: Monroe County Outdoors.”