Swallows are a migrant bird. They begin arriving in the southern part of the USA around March, and by April they have reached the northern states. They are very territorial and will always come back to the same nesting site. They make their nests from mud pellet which attach to structures’ vertical walls, to the frustration of homeowners and buildings maintenance staff. Since swallows are a protected species, once they start laying their eggs, they have to be left alone.