Meeting Abstract
Birds stabilize head position with respect to the body to reduce retinal image blur during flapping flight. Relative head stabilization is needed because the vertical position of the body changes continuously during flapping flight. It rises and falls substantially due to the differences in lift force generated during the down- and upstroke of the wing. While bird head-bobbing during walking and whole-body stabilization on an oscillating perch have been studied, little is known about how birds accomplish head stabilization during flapping flight. To address the challenge of dissecting avian head stabilization, we decided to start out by ignoring the daunting anatomical complexity of the avian neck. We approximated it with a one-dimensional mass-spring-damper system for vertical displacements. We corroborated the model’s dimensionless natural frequency and damper coefficient from high-speed video recordings of Whooper Swans (Cygnus cygnus) flying in their natural environment. The vertical body position was used as input and the vertical head position as output of the unknown transfer function of the neck. Remarkably, we find that the neck can be accurately modeled as a spring without damper. This suggests that avian head stabilization is passive within a wing beat. Our finding alludes to a solution for stabilizing cameras on bioinspired robots with similar large body oscillations induced by flapping wings: image blur can be much reduced by mounting the camera on a well-tuned spring.
