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 ...