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.

鸣唱对唱（Duetting）是一种集体协作行为，可兼具多重功能，例如联合领地防御与配偶守卫。解析鸟类鸣唱适应功能的核心步骤之一，便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，仅雄性鸣唱的鸟类类群的季节性鸣唱模式，与鸣唱对唱类群的季节性模式存在显著差异——这是由于鸣唱功能会因性别、鸣唱角色（发起者与应答者）以及对唱组织层级（个体层面与配对层面）的不同而发生变化。本研究旨在探究鸣唱对唱的季节性变化模式是否受上述因素影响，若存在影响，则意味着对鸣唱功能的解读需进行针对性区分。我们针对新热带界鸟类物种棕灶鸟（rufous hornero *Furnarius rufus*）的配对配偶群体开展了连续7个月的观测，记录其鸣唱与领地行为。整体而言，配对双方有61%的鸣唱会被协调为对唱，且多项鸣唱特征（鸣唱发起频率、鸣唱总量与对唱频率）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发生领地互动，发起更多鸣唱，且按比例应答伴侣鸣唱的次数也更多。雄性的鸣唱发起频率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，两性应答伴侣鸣唱的速度更快、应答频率也更高。配对双方的对唱频率在繁殖前期与繁殖后期均有所提升。最后，鸣唱发起频率与对唱频率（而非鸣唱应答频率），与陌生个体发生领地互动的频次呈显著相关。尽管本研究结果表明，鸣唱功能可能会因性别、鸣唱角色及对唱组织层级的不同而存在差异，但整体而言，棕灶鸟的鸣唱对唱功能主要为保卫共同领地，以及作为双方共同的配偶守卫策略。