“Barn Swallow” is simply another name for cliff swallows; they are the same bird. They earned this nickname because they are commonly found living in mud nests at the top of the exterior walls of wooden or concrete barns.
Barns typically have high walls, and in some ways these walls resemble the cliffs that the birds’ ancestors originally dwelt in. Barn swallows like to be up high, and they feel safe and protected under the eaves.
Barn swallows are migratory birds. They construct nests on barns and live there for a season, then continue on their migratory path and return the next year. Each year, their population grows. It can be fun to watch a few barn swallows build their unique nests on a barn wall, but the trouble is that the population can double or even triple each year. What was once pleasant and interesting to observe becomes a filthy, out of control infestation.
It is better to encourage the birds to live somewhere else early, before they make up their minds to stay. Allstate Bird and Animal Control offers barn swallow repellent, which is a unique mixture specially formulated for these birds.