Johansson L C, Lindhe Norberg U M
Department of Zoology, Göteborg University, Box 463, SE-405 30 Göteborg, Sweden.
J Exp Biol. 2001 May;204(Pt 10):1687-96. doi: 10.1242/jeb.204.10.1687.
To examine the hydrodynamic propulsion mechanism of a diving great crested grebe (Podiceps cristatus), the three-dimensional kinematics was determined by digital analysis of sequential video images of dorsal and lateral views. During the acceleration phase of this foot-propelled bird, the feet move through an arc in a plane nearly normal to the bird's line of motion through the water, i.e. the toes move dorsally and medially but not caudally relative to the water. The kinematics of the grebe's lobed feet is different from that in anseriforms, whose feet move in a plane mostly parallel to the bird's line of progress through the water. Our results suggest that the foot-propelled locomotor mechanism of grebes is based primarily on a lift-producing leg and foot stroke, in contrast to the drag-based locomotion assumed previously. We suggest that the lift-based paddling of grebes considerably increases both maximum swimming speed and energetic efficiency over drag-based propulsion. Furthermore, the results implicate a new interpretation of the functional morphology of these birds, with the toes serving as a self-stabilizing multi-slotted hydrofoil during the power phase.
为研究风头䴙䴘（Podiceps cristatus）的水动力推进机制，通过对背视图和侧视图的连续视频图像进行数字分析来确定其三维运动学。在这种用脚推进的鸟类的加速阶段，双脚在一个几乎垂直于鸟类在水中运动方向的平面内做弧形运动，即相对于水而言，脚趾向背侧和内侧移动，但不向尾侧移动。䴙䴘有蹼的脚的运动学与雁形目鸟类不同，雁形目鸟类的脚在一个大致平行于鸟类在水中前进方向的平面内运动。我们的研究结果表明，与之前假设的基于阻力的运动方式不同，䴙䴘用脚推进的运动机制主要基于产生升力的腿部和脚部划水动作。我们认为，与基于阻力的推进方式相比，䴙䴘基于升力的划水动作极大地提高了最大游泳速度和能量效率。此外，研究结果还对这些鸟类的功能形态学提出了一种新的解释，即在动力阶段，脚趾起到了自稳定的多槽水翼的作用。
