Loud mechanical sounds with a communication role are called sonations. Male Subtropical Doraditos (Pseudocolopteryx acutipennis) exhibit five conspicuously modified primaries suspected of sonating. Here we 1) describe feather modifications, 2) describe three different territorial/aggressive contexts for these sounds: One-perch aerial displays, Two-perch aerial displays and Chukrut pursuits, 3) investigate the kinematics of the most common display (One-perch aerial display) and the physical mechanisms of sonation using synchronized high-speed video and audio, and 4) assess the roles of modified wing feathers in all contexts by experimental manipulation in four individuals. Primaries p3 to p7 were modified in adult males but not in females: p3 was pointed with a reduced distal third to the outer vane; p4 and p5 were slim and falciform with pointed tips curved outwards; p6 was broad, massive and subtly S-shaped, with a spatulate tip; and p7 was large with the distal third of the outer vane abruptly reduced, and the inner vane with a shallow concave sub-apical emargination. One-perch aerial displays consisted of perched short nasal introductory syllables accelerating until the bird performed a super-rapid circular flight of ∽15 cm in diameter from and to the same branch, during which two syringeal syllables and three mechanical syllables (chik… chik…. chik-chik frrrottt). The syllables were produced during rapid downstrokes by fluttering feathers and were bisonic, being conformed by two simultaneous main tonal, flat, narrow band sounds: a low-pitched note (f0 ∽c. 1 kHz) and a high-pitched note (f0 ∽c. 3.7 kHz). p7 is the necessary and sufficient sound source of the low-pitched note (removal of p7 caused the sound to disappear) and p3 is the sound source of the high-pitched note, being necessary but perhaps not sufficient (removal of p3 caused the sound to disappear); the other modified feathers seem involved in different roles related to either producing the sonation (p4 and p5 interacting with p3) or allowing it (p6 raising dorsally letting p7 flutter freely; removal of p6 did not affect sound production). The specialized shape of p6 might be compromised to allow sonation of p7 without losing flight functionality. Sonations in Subtropical Doraditos occupy the position of the vocal flourish in the songs of other Pseudocolopteryx suggesting the evolutionary replacement of vocal by mechanical sounds. We propose that wing songs in flying birds may be constrained to occur in temporally broken patterns due to intrinsic features of flapped flight and structurally constrained by the demands of creating an airfoil.

中文翻译：

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亚热带 Doradito (Pseudocolopteryx acutipennis) 空中展示中的双声机械翼歌和复杂的运动学

具有交流作用的响亮的机械声音被称为超音波。雄性亚热带 Doraditos (Pseudocolopteryx acutipennis) 表现出五个明显改变的初选，怀疑有声波。在这里，我们 1) 描述羽毛修改，2) 描述这些声音的三种不同的领土/攻击性上下文：单栖空中展示、两栖空中展示和 Chukrut 追击，3) 研究最常见展示（单栖）的运动学空中显示）和使用同步高速视频和音频的声波物理机制，以及 4）通过对四个人的实验操作来评估修改后的翼羽在所有情况下的作用。成年雄性中的初级 p3 至 p7 被修改，但在雌性中未发生改变：p3 指向外叶片的远端三分之一处减少；p4 和 p5 细长镰刀状，尖端向外弯曲；p6 宽、大、呈微妙的 S 形，尖端呈匙形；p7 大，外叶片的远端三分之一突然缩小，内叶片具有浅凹的亚顶微缺。单栖空中显示由栖息的短鼻引导音节组成，直到鸟在同一分支之间进行直径 ∽15 厘米的超快速圆形飞行，在此期间，两个注射器音节和三个机械音节（chik…chik… .chik-chik frrrottt）。这些音节是在快速向下击打过程中通过飘动的羽毛产生的，是双音的，由两个同时出现的主要音调、平坦、窄带声音构成：一个低音调 (f0 ∽c. 1 kHz) 和一个高音 (f0 ∽ c. 3.7 kHz）。p7 是低音音符的必要和充分声源（去除 p7 导致声音消失），p3 是高音音符的声源，必要但可能不充分（去除 p3 导致声音消失）消失）；其他修饰的羽毛似乎参与了与产生共鸣（p4 和 p5 与 p3 相互作用）或允许它（p6 向背抬起让 p7 自由颤动；去除 p6 不影响声音产生）相关的不同角色。p6 的特殊形状可能会受到影响，以允许 p7 发声而不会失去飞行功能。亚热带 Doraditos 中的声音在其他 Pseudocolopteryx 的歌曲中占据了声乐繁荣的位置，这表明机械声音在进化上取代了声乐。