Data from: Singing behaviour of Ruby-crowned Kinglets (Regulus calendula) in relation to time-of-day, time-of-year, and social context

Observational field studies provide insight on the multifunctional nature of birdsong. For example, if song production were limited to pre-fertilization, then that would suggest a mate attraction function. If it were used throughout the breeding season and in response to intruding males, then that would suggest a territorial defence function. In the present study, we determined the daily and seasonal singing patterns of male Ruby-crowned Kinglets (Regulus calendula) in Labrador, Canada, using microphone arrays in two breeding seasons. Using a playback experiment, we simulated a territorial intrusion to compare the structure of songs produced while defending a territory to the structure of songs produced during solo and contest singing. Singing peaked in the early part of the breeding season and then declined continuously for the remainder of the season, which suggests that the songs function in mate attraction. Singing peaked 2-3 h after dawn, and then declined steadily until it stopped at 2200 h. Some nocturnal singing was observed, but no dawn singing was observed. A high probability of signal overlap by heterospecific songs at dawn would hinder signal recognition and explain the observed delay in peak singing activity. Vocal responses to playback suggested a function in territory defence. However, there were no significant differences in the duty cycle, frequency modulation, and bandwidth of songs in relation to the context of song production, though songs were shorter in the intrusion context than during solo singing. Overall, the study provides the first quantitative description of the effects of time of day, time of year, and social context on singing behaviour in this understudied species.

野外观察研究可为揭示鸟鸣的多重功能属性提供重要视角。例如，若鸣唱仅局限于受精前阶段，则可推断其功能为吸引配偶；若鸣唱贯穿整个繁殖季且用于应对入侵雄鸟，则可推断其具备领地防御功能。本研究于加拿大拉布拉多地区开展，在两个繁殖季中利用麦克风阵列（microphone array）记录了红冠戴菊（Ruby-crowned Kinglet，Regulus calendula）雄鸟的日节律与季节节律鸣唱模式。本研究通过回放实验模拟领地入侵场景，对比分析领地防御鸣唱、独处鸣唱与争斗鸣唱的结构差异。鸣唱活动在繁殖季初期达到峰值，随后在整个繁殖季剩余阶段持续下降，这一结果表明鸣唱的功能为吸引配偶。鸣唱峰值出现在日出后2-3小时，随后平稳下降直至当日22:00完全停止。研究中观测到少量夜间鸣唱，但未发现黎明前鸣唱行为。黎明时段异种鸣唱造成信号重叠的概率较高，这会干扰信号识别，也可解释本研究中观测到的鸣唱峰值延迟现象。对回放实验的声学响应结果表明鸣唱具备领地防御功能。不过，尽管入侵场景下的鸣唱时长较独处鸣唱更短，但不同鸣唱场景下的鸣唱占空比、频率调制（frequency modulation）与带宽（bandwidth）均无显著差异。总体而言，本研究首次针对这种尚未被充分研究的鸟类，定量描述了日时段、季节时段与社会场景对其鸣唱行为的影响。