Barn swallows live in outdoor structures such as barns, under bridges and in outbuildings. The birds build nests close to the ceilings of these structures out of mud, hay, horsehair, feathers and small twigs. It is possible to entice barn swallows to live in a nest that has already been constructed if they have the ability to enter and leave the building freely. They need a regular source of food from insects, so avoid using pesticide on your lawn or near the structure in order to keep them around.
Place 5-by-3-inch wood shelves 5 1/2 inches under the ceiling. The shelves should be made out of rough-cut wood so that the swallows can adhere mud to the surface.
Build a nesting cup out of a straight piece of rough wood and a curved piece of rough wood that can be adhered to it. Purchase a semicircle of wood from a hardware or home store and use an electric drill to attach it to the straight piece of wood. The exact size is not important, but the nesting cup should be big enough to fit four to five eggs and an adult swallow. Attach the nesting cup to the shelf to attract barn swallows.
Place newspaper under each nest so that bird droppings can be easily cleaned up once birds are living in the nest. Place a tray of mud outside of the building so that the swallows can easily create their nest.