Promiscuity, inbreeding and dispersal propensity in great tits

► Avian extrapair mating is hypothesized to act as a means of inbreeding avoidance. ► We tested whether parental relatedness influences brood paternity in great tits. ► There were fewer extrapair young (EPY) in inbred than in outbred broods. ► Inbreeding and locally born females had fewer EPY than immigrant females. ► Large-scale dispersal behaviour may influence the promiscuity-inbreeding link.