The Delichon martins were originally cliff nesters, breeding in colonies situated under an overhang on a vertical cliff.
However, the house martin now largely uses human structures, as, to a lesser extent, does the Asian house martin.
The typical nest is a grass or feather-lined deep closed mud bowl with a small opening at the top, but many Asian house martins leave the top of the nest open.

David Winkler and Frederick Sheldon believe that evolutionary development in the mud-building swallows, and individual species follow this order of construction.
A retort builder like red-rumped swallow starts with an open cup, closes it, and then builds the entrance tunnel.
Winkler and Sheldon propose that the development of closed nests reduced competition between males for copulations with the females.
Since mating occurs inside the nest, the difficulty of access means other males are excluded.
This reduction in competition permits the dense breeding colonies typical of the Delichon martins.

The urban common house martin has to compete with house sparrows, which frequently attempt to take over the nest during construction, with the house martins rebuilding elsewhere if the sparrows are successful.
The entrance at the top of the completed cup is so small that the sparrows cannot take over the nest once it is finished.

As with other swallows, pairing and copulation displays are normally brief, taking just a few minutes.
The male calls to a female and attempts to lead her to the nest, where he lands and continues calling while posing with lowered head, dropped wings and ruffled throat.
If he is successful, the female calls and allows him to mount her, usually in the nest.
Three or four white eggs are the normal clutch and all three species are frequently double-brooded.
Both sexes build the nest, incubate the eggs and feed the chicks, although the female does most of the incubation, which normally lasts 14–16 days.
The newly hatched chicks are altricial, and after a further 22–32 days, depending on weather, the chicks leave the nest.
The fledged young stay with, and are fed by, the parents for about a week after leaving the nest.
Occasionally, young birds from the first brood will assist in feeding the second brood.

A Scottish study showed that mortality in common house martins occurred mostly outside the breeding season and averaged 57%.
Females that had raised two clutches in a season had a higher mortality than those that were single-brooded, but there was no such correlation for the males.
The Delichon martins were originally cliff nesters, breeding in colonies situated under an overhang on a vertical cliff. However, the house martin now largely uses human structures, as, to a lesser extent, does the Asian house martin. The typical nest is a grass or feather-lined deep closed mud bowl with a small opening at the top, but many Asian house martins leave the top of the nest open.
David Winkler and Frederick Sheldon believe that evolutionary development in the mud-building swallows, and individual species follow this order of construction. A retort builder like red-rumped swallow starts with an open cup, closes it, and then builds the entrance tunnel. Winkler and Sheldon propose that the development of closed nests reduced competition between males for copulations with the females. Since mating occurs inside the nest, the difficulty of access means other males are excluded. This reduction in competition permits the dense breeding colonies typical of the Delichon martins.
The urban common house martin has to compete with house sparrows, which frequently attempt to take over the nest during construction, with the house martins rebuilding elsewhere if the sparrows are successful. The entrance at the top of the completed cup is so small that the sparrows cannot take over the nest once it is finished.
As with other swallows, pairing and copulation displays are normally brief, taking just a few minutes. The male calls to a female and attempts to lead her to the nest, where he lands and continues calling while posing with lowered head, dropped wings and ruffled throat. If he is successful, the female calls and allows him to mount her, usually in the nest. Three or four white eggs are the normal clutch and all three species are frequently double-brooded. Both sexes build the nest, incubate the eggs and feed the chicks, although the female does most of the incubation, which normally lasts 14–16 days. The newly hatched chicks are altricial, and after a further 22–32 days, depending on weather, the chicks leave the nest. The fledged young stay with, and are fed by, the parents for about a week after leaving the nest. Occasionally, young birds from the first brood will assist in feeding the second brood.
A Scottish study showed that mortality in common house martins occurred mostly outside the breeding season and averaged 57%. Females that had raised two clutches in a season had a higher mortality than those that were single-brooded, but there was no such correlation for the males.
Delichon