Concord Field Station, Department of Organismic and Evolutionary Biology, Harvard University, Bedford, MA 01730, USA
Concord Field Station, Department of Organismic and Evolutionary Biology, Harvard University, Bedford, MA 01730, USA.
J Exp Biol. 2018 Oct 11;221(Pt 19):jeb168831. doi: 10.1242/jeb.168831.
Loons (Gaviiformes) are arguably one of the most successful groups of swimming birds. As specialist foot-propelled swimmers, loons are capable of diving up to 70 m, remaining underwater for several minutes, and capturing fish. Despite the swimming prowess of loons, their undomesticated nature has prevented prior quantitative analysis. Our study used high-speed underwater cameras to film healthy common loons () at the Tufts Wildlife Clinic in order to analyze their swimming and turning strategies. Loons swim by synchronously paddling their feet laterally at an average of 1.8 Hz. Combining flexion-extension of the ankle with rotation at the knee, loon swimming resembles grebe swimming and likely generates lift forces for propulsion. Loons modulate swimming speed by altering power stroke duration and use head bobbing to enhance underwater vision. We observed that loons execute tight but slow turns compared with other aquatic swimmers, potentially associated with hunting by flushing fish from refuges at short range. To execute turns, loons use several strategies. Loons increase the force produced on the outside of the turn by increasing the speed of the outboard foot, which also begins its power stroke before the inboard foot. During turns, loons bank their body away from the turn and alter the motion of the feet to maintain the turn. Our findings demonstrate that foot-propelled swimming has evolved convergently in loons and grebes, but divergently from cormorants. The swimming and turning strategies used by loons that allow them to capture fish could inspire robotic designs or novel paddling techniques.
潜鸟（鸊鷉目）可说是最成功的游泳鸟类之一。作为专业的足部推进式游泳者，潜鸟能够潜水至 70 米深，在水下停留数分钟，并捕捉鱼类。尽管潜鸟的游泳能力很强，但由于它们的野生习性，之前无法进行定量分析。我们的研究使用高速水下摄像机拍摄了图夫茨野生动物诊所健康的普通潜鸟（），以分析它们的游泳和转弯策略。潜鸟通过以平均 1.8 Hz 的速度同步横向划动它们的脚来游泳。通过踝关节的屈伸与膝关节的旋转相结合，潜鸟的游泳方式类似于䴙䴘的游泳方式，可能会产生推进力。潜鸟通过改变动力冲程的持续时间来调节游泳速度，并利用头部的摆动来增强水下视力。我们观察到，与其他水生游泳者相比，潜鸟的转弯动作紧凑但速度较慢，这可能与它们在短距离内从避难所中驱赶鱼类有关。为了执行转弯，潜鸟使用了几种策略。潜鸟通过增加外脚的速度来增加转弯外侧产生的力，外脚的动力冲程也比内脚更早开始。在转弯过程中，潜鸟将身体从转弯处倾斜，并改变脚的运动来保持转弯。我们的研究结果表明，足部推进式游泳在潜鸟和䴙䴘中已经趋同进化，但与鸬鹚不同。潜鸟用来捕捉鱼类的游泳和转弯策略可能会启发机器人设计或新的划桨技术。
