revision preference src: This swallow is socially monogamous, with some extra-pair mating. About 15 % of nestlings and about 25 % of broods are developed through extra-pair paternity. <SEP> tgt: This swallow is socially monogamous, with some extra-pair mating. For example, about 15 % of nestlings and about 25 % of broods are developed through extra-pair paternity.