Department of Biological Sciences, University of Illinois at Chicago, 845 West Taylor Street (MC066), Chicago, IL 60607, USA.
SELVA: Investigación para la Conservación en el Neotrópico, Diagonal 42a No 20-37, Bogotá, Colombia.
Integr Comp Biol. 2020 Nov 1;60(5):1147-1159. doi: 10.1093/icb/icaa115.
Sonations are sounds that animals produce with structures other than the vocal apparatus for communication. In birds, many sonations are usually produced with modified flight feathers through diverse kinematic mechanisms. For instance, aeroelastic fluttering of feathers produces tonal sound when airflow exceeds a threshold velocity and induces flight feathers to oscillate at a constant frequency. The Fork-tailed flycatcher (Tyrannus savana) is a Neotropical bird with both migratory and year-round resident subspecies that differ in the shape of the outer primary feathers of their wings. By integrating behavioral observations, audio recordings, and high-speed videos, we find that male Fork-tailed flycatchers produce sonations with their outer primary feathers P8-10, and possibly P7. These sounds are produced during different behavioral contexts including: the pre-dawn display, intraspecific territorial disputes, when attacking potential nest predators, and when escaping. By placing feathers in a wind tunnel, we elicited flutter at frequencies that matched the acoustic signature of sounds recorded in the wild, indicating that the kinematic mechanism responsible for sound production is aeroelastic flutter. Video of wild birds indicated that sonations were produced during the downstroke. Finally, the feathers of migratory (T.s.savana) and year-round resident (T.s.monachus) Fork-tailed flycatchers flutter in feather locations that differ in shape between the subspecies, and these shape differences between the subspecies result in sounds produced at different frequencies.
鸟鸣是动物通过非发声器官发出的声音，用于交流。在鸟类中，许多鸟鸣通常是通过改变飞行羽毛通过不同的运动学机制产生的。例如，当气流超过阈值速度并诱导飞行羽毛以恒定频率振荡时，羽毛的空气弹性颤动会产生音调声音。叉尾蜂鸟（Tyrannus savana）是一种新热带鸟类，具有迁徙和常年居留的亚种，它们翅膀的外初级飞羽形状不同。通过整合行为观察、音频记录和高速视频，我们发现雄性叉尾蜂鸟用它们的外初级飞羽 P8-10 产生鸟鸣声，可能还有 P7。这些声音是在不同的行为背景下产生的，包括：黎明前的展示、种内领地争端、攻击潜在的巢捕食者时，以及逃跑时。通过将羽毛放在风洞中，我们在与野外记录的声音的声学特征相匹配的频率下诱发了颤动，表明产生声音的运动学机制是空气弹性颤动。野生鸟类的视频显示，鸟鸣声是在向下划动时产生的。最后，迁徙（T.s.savana）和常年居留（T.s.monachus）叉尾蜂鸟的羽毛在亚种之间的形状不同的羽毛位置上颤动，亚种之间的这些形状差异导致产生不同频率的声音。
