Duetting behavior varies with sex, season, and singing role in a tropical oriole (Icterus icterus)

Females and males of many animals combine their vocalizations into coordinated acoustic duets. Duets can mediate both cooperation and conflict between partners, and are common in tropical, sedentary species that may use duets for multiple functions year-round. To elucidate the full range of duet functions, we need to study the individual-level behaviors that generate duets throughout the year. We evaluated multiple functions of duetting behavior in female and male Venezuelan troupials (Icterus icterus) during the breeding and non-breeding seasons, including territory defense, maintaining contact with a mate, and paternity guarding. In both sexes during both seasons, song initiation rates were predicted by conspecific solo and duet rates. However, troupials were more likely to answer their mate to form duets after conspecific duets than after conspecific solos, supporting a territory defense function of duets. Troupials that answered their mate to form duets were also more likely to move toward their mate (than duet initiators and soloists), suggesting that duet participation also functions to maintain contact. During the breeding season, males were particularly likely to fly toward their mate after answering to form a duet. This finding may indicate that males answer to guard paternity, although other predictions of paternity guarding are not supported. Examining individual-level behaviors during both the breeding and non-breeding season revealed multiple functions of troupial duets. Our results are consistent with social selection acting on females and males to maintain contact and territories year-round, and possibly sexual selection on males for functions tied to the breeding season.

诸多动物的雌雄个体可通过结合各自鸣唱，形成协同声学二重唱（acoustic duets）。二重唱可介导伴侣间的合作与冲突，且在热带定居性物种中较为常见，这类物种全年可将二重唱用于多种功能。为阐明二重唱的全部功能范畴，我们需要对全年产生二重唱的个体层面行为展开研究。我们在繁殖季与非繁殖季期间，对委内瑞拉拟鹂（Icterus icterus）雌雄个体的二重唱行为的多项功能进行了评估，评估维度涵盖领地防御、与配偶保持联系以及父权保障。无论雌雄个体，在两个季节中，其鸣唱发起率均可由同种个体的独唱与二重唱率预测。然而，相较于同种个体的独唱场景，委内瑞拉拟鹂在听到同种个体的二重唱后，更易回应配偶以形成二重唱，这一结果支持了二重唱的领地防御功能。回应配偶以形成二重唱的拟鹂个体，相较于二重唱发起者与独唱者，也更有可能向配偶移动，这表明参与二重唱同时也承担着维持联系的功能。在繁殖季，雄性个体在回应配偶形成二重唱后，尤其倾向于飞向配偶。尽管父权保障的其他预测未得到支持，但这一发现或表明雄性个体通过回应配偶以实现父权保障。对繁殖季与非繁殖季的个体层面行为进行分析，揭示了委内瑞拉拟鹂二重唱的多项功能。我们的研究结果支持：社会选择作用于雌雄个体以使其全年维持联系与领地，同时雄性个体可能因与繁殖季相关的功能而受到性选择。