Aerodynamic performance appears to have shaped the evolution of flight-feather microstructures

2. Abstract Flight feather structures - shaft, barbs, and barbules - have transformed through evolution. Although size, shape and orientation of these structures likely influence the aerodynamic performance of the feathers, their impact remains unclear. Here we investigated the feather structures’ influence on flow and aerodynamic performance, using computational fluid dynamic modelling, by modifying the morphology of a section of a Jackdaw ( Corvus monedula ) flight feather. We show that the flow over the leading vane is a key factor, and that changing the barb-to-shaft angle from its natural state as well as the trailing vane barb angle, reduces performance, which could explain evolutionary changes from early Paraves species. All in all, our results suggest that current feather composition may be close to a local maximum for both aerodynamic efficiency and stability/flow predictability, suggesting evolution of feather structures have been driven by aerodynamic performance, which should have implications for designing bio-inspired technologies.