Surprisingly, one way that such males can acquire a mate is to kill the young nestlings and then pair with the female who has to start a new family. One observer watched a male remove a whole brood by picking up each nestling, flying some distance away and then dropping it on the ground. After breeding swallows gather in communal roosts, sometimes thousands strong. Reedbeds are regularly favoured. The birds give spectacular pre-roosting displays, bunching tougher and towering higher and even higher before swerving and swirling en masse before swooping low over the reeds.
Swallows are able to obtain food while migrating.
Unlike most other passerines they are diurnal migrants, travelling at almost ground level and skimming the waves whereas most migrants move at a height of several thousand feet. To drink, these graceful birds skim low over the surface scooping water with open mouths. Swallows usually nest close to man. On occasions pairs occupy the same building with nests as close as a yard apart. In dry conditions when wet mud is difficult to obtain swallows will take over old nests of other birds including house martins and blackbirds.