Duetting, extra-pair paternity and reproductive success in the Rufous Hornero

Although intensively studied, we still have little consensus about the direct fitness consequences of vocal duetting. Some studies suggest that duetting functions in acoustic mate guarding to prevent cuckoldry, whereas other studies argue that duetting is a cooperative behavior to defend common territories. Thus, duetting parameters presumably could reflect territory quality and a pair’s reproductive success. We investigated extra-pair paternity and the relation among song traits, territory quality and reproductive success in the rufous hornero (Furnarius rufus), a Neotropical, socially monogamous bird. We found a lower than average rate of extra-pair paternity (3.33% of 120 offspring and 6.52% of 46 broods), and 100% apparent nest success. Female song (rate, output and latency to answer partner-initiated song) was positively correlated with territory size and quality, as reflected in amount and proportion of territory foraging patches. Duet duration, but not rate, was positively correlated with territory size. Our results suggest that female song and the pair duet are used in the defense of food resources within territories, or enable the acquisition of high quality and large territories. However, neither features of female song, male song, or duets, nor territory features correlated with reproductive success (number of social fledglings and post-fledging survival) in this species, suggesting that song or territory might affect fitness in other ways, such as in juvenile development or adult survival.