Meeting Abstract
Birds appear to transition smoothly from aerial to terrestrial environments via take-off and landing. These transitions are presumably under high selective pressures, including events such as predation evasion, hunting, and avoiding wing damage. Take-off and landing occur on substrates with often-unpredictably varying levels of compliance. Previous work describes avian leg and wing modules as functionally distinct, with slight overlap during these critical transition phases. We conducted experiments to test the effects of perch compliance upon module coordination. We predicted varying compliance would require modulation of both wing and leg activity. Surprisingly, the birds did not modulate leg activity in response to compliance during takeoff, whereas they did during landing. During take-off on compliant perches, smaller leg peak forces and application times cause lower initial flight velocity. Birds partially compensate for this deficit using their wings after leaving the perch. In contrast, birds have the same flight velocity at touchdown regardless of known perch compliance. Unlike during take-off, birds vary peak leg force inversely with time of force application, indicating work absorption by the legs is modulated. Therefore we suggest that legs and wings operate as functionally distinct modules during transitions to and from flight. These experiments provide new insight into how control strategies differ between take-off and landing.
