Data from: Female collared flycatchers choose neighbouring and older extra-pair partners from the pool of males around their nests

Extra-pair copulation is common among passerine birds. Females might engage in this behavior to obtain direct or indirect benefits. They may choose extra-pair males with larger ornaments, especially if they are costly to produce. Here we studied extra-pair paternity in the collared flycatcher. Genetic analysis allowed us to identify the presence or absence of extra-pair young in the focal nests, and to identify extra-pair fathers. We also identified potential males available as extra-pair sires around the nests of females who had extra-pair young. First, we tested the relationship between paternity in own nest and ornament size (wing patch and/or forehead patch), morphological traits and age of social males and females. Second, we compared the same suite of traits among social mates, extra-pair males and all potential extra-pair mates. Finally, we investigated the effect of the size of ornaments on the distance between the social nest and that of nest the extra-pair father. Contrary to our prediction, males with larger ornaments and longer wings lost more paternity in their nests. We also found that early breeders lost less paternity in their nests. Extra-pair males were older and had longer wings than social and potential extra-pair males. Females mainly obtained extra-pair mates near their nests but the distance did not vary according to ornamentation. These results could potentially be explained by differences in mate guarding strategy as older males may be more experienced in guarding their mate and attract other females more easily. More data about mate guarding and prospecting are needed to increase our understanding of mechanisms underlying the extra-pair paternity in birds