Data from: Duetting behavior in a Neotropical ovenbird: sexual and seasonal variation and adaptive signaling functions

Duetting is a collective behavior and might have multiple functions, including joint territory defense and mate guarding. An important step toward understanding the adaptive function of bird song is to determine if and how singing behavior varies seasonally. However, seasonal patterns for duetting species are different from the pattern described for species in which only the male sings, because song function may vary according to sex, singing role (initiator vs. responder) and level of duet organization (individual vs. pair). We investigated whether patterns of seasonal variation in duetting depends on these factors, which would suggest different interpretations of song function. We studied social pairs of a Neotropical bird species (rufous hornero Furnarius rufus) for seven consecutive months, recording vocal and territorial behaviors. Overall, partners coordinated 61% of their songs into duets and many song traits (song initiation rate, song output and duet rate) peaked in territorial contexts. Males engaged in territorial interactions with strangers more often, initiated more songs, and answered proportionately more of their partners’ songs than females. Male song initiation rate peaked during the pre- and post-breeding stages, whereas females initiated more songs during the non-breeding season. Both sexes answered partner songs faster and at higher rates during the pre-breeding and female fertile stages. Partners duetted at a higher rate during the pre- and post-breeding stages. Finally, song initiation rates and duet rate, but not song answering rates, correlated with frequency of territorial interactions with strangers. Although our findings indicate that song function may vary with sex, singing role and level of duet organization, our results suggest that in general duet functions to defend common territories and as a mutual mate guarding strategy in the rufous hornero.

对鸣行为（duetting）是一种协同行为，可能具备多重功能，包括共同领地防御与配偶守卫。探究鸟类鸣唱适应功能的关键一环，是明确鸣唱行为是否存在季节性变化，以及其变化的具体模式。然而，对鸣物种的季节性鸣唱模式与仅雄性鸣唱的物种存在显著差异，因为鸣唱功能可能随性别、鸣唱角色（发起者与应答者）以及对鸣组织层级（个体层面与配对层面）发生变化。本研究旨在探究对鸣的季节性变化模式是否受上述因素影响，这一探究将为解读鸣唱功能提供不同视角。我们对新热带界鸟类物种棕灶鸟（rufous hornero，*Furnarius rufus*）的社会配对个体进行了连续7个月的观测，记录其鸣唱与领地行为。总体而言，配对双方61%的鸣唱会协同形成对鸣；多项鸣唱特征（鸣唱发起频次、鸣唱总量与对鸣频次）在领地互动场景中达到峰值。相较于雌性，雄性更频繁地与陌生个体开展领地互动，发起更多鸣唱，且应答伴侣鸣唱的比例也更高。雄性的鸣唱发起频次在繁殖前期与繁殖后期达到峰值，而雌性则在非繁殖季发起更多鸣唱。在繁殖前期与雌性发情期，雌雄双方应答伴侣鸣唱的速度更快、频次更高。配对双方在繁殖前期与繁殖后期的对鸣频次更高。最后，鸣唱发起频次与对鸣频次（而非鸣唱应答频次）与陌生个体间的领地互动频次呈显著相关。尽管本研究结果表明鸣唱功能会随性别、鸣唱角色及对鸣组织层级发生变化，但整体而言，棕灶鸟的对鸣功能仍以保卫共同领地与双向配偶守卫为主。