The nesting area is defended early in the nesting period. Breeding The nesting area is defended early in the nesting period. The males are usually the first to arrive at the nesting site, passing the females on the way. However, if paired before the arrival, the female will keep watch at the site entrance while the male continues digging. While finishing up the nest, the male puts on a show for the females.
Bank swallows are socially monogamous.
Males are attracted to heavier females. The clutch size averages between 2 to 7 eggs, with only one brood per year. Males take over when females leave the nest. Incubation periods range from 13 to 15 days. There is rapid growth in the first 6 to 8 days, escpeially with the tarsi.