Whole-body 3D kinematics of bird take-off: key role of the legs to propel the trunk
Résumé
Previous studies showed that birds primarily use their hindlimbs to propel themselves into the air in order to takeoff. Yet, it remains unclear how the different parts of their musculoskeletal system move to produce the necessary acceleration. To quantify the relative motions of the bones during the terrestrial phase of takeoff , we used biplanar fluoroscopy in two species of birds, diamond dove (Geopelia cuneata) and zebra finch (Taeniopygia guttata). We obtained a detailed 3D kinematics analysis of the head, the trunk and the three long bones of the left leg. We found that the entire body assisted the production of the needed forces to takeoff , during two distinct but complementary phases. The first one, a relatively slow preparatory phase, started with a movement of the head and an alignment of the different groups of bones with the future takeoff direction. It was associated with a pitch down of the trunk and a flexion of the ankle, of the hip and, to a lesser extent, of the knee. This crouching movement could contribute to the loading of the leg muscles and store elastic energy that could be released in the propulsive phase of takeoff , during the extension of the leg joints. Combined with the fact that the head, together with the trunk, produced a forward momentum, the entire body assisted the production of the needed forces to takeoff. The second phase was faster with mostly horizontal forward and vertical upward translation motions, synchronous to an extension of the entire lower articulated muscu-loskeletal system. It led to the propulsion of the bird in the air with a fundamental role of the hip and ankle joints to move the trunk upward and forward. Takeoff kinematics were similar in both studied species, with a more pronounced crouching movement in diamond dove, which can be related to a large body mass compared to zebra finch.
Domaines
Sciences du Vivant [q-bio]
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