Stability and dynamics of avian jumping take-off

A jumping take-off is an effective means of becoming airborne: using the legs to push from the ground generates greater body accelerations with reduced energy consumption compared to using aerodynamic forces on wings. The apparent ease with which a bird performs this efficient maneuver stems from the perceived success rate of jumps in nature. But attempts to recreate this process through theoretical or experimental models reveal numerous possible modes of failure, including slipping, toppling, and tumbling. In this study we develop analytical and computational models that explain these failure modes, and propose how they are avoided by birds in nature. We illustrate both successful and failed jumps using simple jumping robots and animations from computer simulation. The computational models incorporate leg kinematics taken from experiments on real jumping animals. Therefore, as a secondary output the model provides quantitative predictions of mechanical forces, torques and power consumption in jumping animals.