This research is an ongoing project that I started during my postdoc at the Max Planck Institute of Animal Behavior in collaboration with the Max Planck Institute of Ornithology. Here we explored how the fine-social structure influences extra-pair mating behavior in monogamous birds. We use a social network approach to characterize the immediate and the indirect social environment of an individual relate to the variation in the pattern of extra-pair paternity among individuals in a group. Some of the questions we are tackling are: Do well connected individuals or highly dense networks favor extra-pair paternity? Does the phenotype of other members of the group influence the extra-pair mating behavior?