From wing shape to fluid dynamics in the barn owl (Tyto alba)

Birds morph their wings and tail in order to glide under a wide range of aerodynamic conditions. Gross wing morphing has been described in a multitude of studies, but the finer details of wing morphing are still unknown. Here, we measured the changes in wing shape and pose in a barn owl, Tyto alba, when gliding across a range of fifteen self-selected speeds. We found that T. alba does not use fine-wing shape control to glide at slow speeds in steady conditions, with the measured wing shapes being highly consistent across all flights. Instead, T. alba relied upon wing postural control (gross pitch) and changes in both tail shape and pose to modulate aerodynamic force. A consistent wing shape provides an exceptional aerodynamic tool for understanding gliding flight in birds through postural change and tail morphing. This geometry was used as the basis for computational fluid dynamics simulations which gave very similar wake measurements and weight support to those measured in flight. This geometry is provided here to assist other researchers interested in exploring the fluid dynamics behind gliding flight in birds.