They build elaborate nests out of mud pellets. They look for sites near a river with dirt embankments. Both cliff and barn swallows pack mud pellets in the upper eaves of a building. The resulting nest will resemble a wine carafe or flask with the opening on the side. They line the nest with grass and feathers. Nests are packed together in close knit colonies. The colonies range in size from a few to several thousand. Cliff and barn swallows have two broods per year with each brood containing four to five eggs. Egg coloration will be

white, cream or pale pink with brown spots on some of the eggs. The eggs take 12 to 14 days to hatch. Fledglings leave the nest after 25 days. They migrate each year between North and South America. They winter in South America and summer in North America.