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.