Do birds detect and respond to forces acting on feathers through filoplumes, which appear to be unique mechanosensory feathers? If filoplumes function as sensors, their morphology should covary with the morphology of their companion feather to better detect feather movements and position. We explore covariation in filoplumes and primaries across 5 species of birds that vary in body size, molt strategy, and the functional life span of their primaries (Green-winged Teal [Anas crecca], Ring-billed Gull [Larus delawarensis], Turkey Vulture [Cathartes aura], Red-tailed Hawk [Buteo jamaicensis], and Red-winged Blackbird [Agelaius phoeniceus]). Filoplumes never extended beyond the coverts and inserted immediately adjacent to the base of their companion primaries, positioning them to detect subtle changes in feather vibration or movement. Far more variation in filoplume number and morphology was due to species differences than to individuals or position in the wing. Across species, filoplume length and number increased with calamus length of primaries. In the 2 species with growing primaries, the number and length of filoplumes were only weakly associated with molting primaries, suggesting that filoplumes were not replaced when their companion primary was replaced. Further, filoplumes associated with a growing primary were not replaced synchronously, leaving others to sense primary position and movement. Finally, filoplume number and length were greatest in Red-tailed Hawks, a species that carries individual feathers for multiple years, but links between filoplume morphology and molt strategy await broader comparative studies. Taken together, the morphology of filoplumes and their replacement schedule relative to their associated primary suggests that they are sensors, capable of detecting subtle differences in the position and movement of their companion feathers.

中文翻译：

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Filoplume 形态与它们的伴侣初级共变，表明它们是羽毛特异性传感器

鸟类是否通过丝状羽（似乎是独特的机械感觉羽毛）检测并响应作用在羽毛上的力？如果丝羽起到传感器的作用，它们的形态应该与其伴生羽毛的形态共同变化，以更好地检测羽毛的运动和位置。我们探讨了 5 种鸟类的丝状羽和初生体的协变，这些鸟类的体型、蜕皮策略和初生体的功能寿命（绿翅蓝绿色 [Anas crecca]、环嘴鸥 [Larus delawarensis]、土耳其秃鹰） [Cahartes aura]、红尾鹰 [Buteo jamaicensis] 和红翅黑鸟 [Agelaius phoeniceus]）。Filoplumes 从未延伸到覆羽之外，并紧邻其伴生初级的基部插入，将它们定位以检测羽毛振动或运动的细微变化。丝羽数量和形态的变化更多是由于物种差异而不是个体或翅膀中的位置。跨物种，丝羽长度和数量随着初生菖蒲长度的增加而增加。在初生植物生长的 2 个物种中，丝状羽的数量和长度仅与蜕皮的初生体有微弱的相关性，这表明当它们的伴侣初级被替换时，丝状羽没有被替换。此外，与生长的初级相关的丝状羽没有同步更换，让其他人感知初级的位置和运动。最后，红尾鹰的毛羽数量和长度最大，红尾鹰是一种携带单根羽毛多年的物种，但毛羽形态与蜕皮策略之间的联系还有待更广泛的比较研究。综合起来，