The role of wind, updrafts and turbulence on flight energetics

Emily Shepard

Swansea University, UK

In 1972 Schmidt Nielsen published his seminal work on the costs of moving in different media, demonstrating that mass-specific costs of transport decrease with body size and are generally lowest for swimming, followed by flight, with terrestrial locomotion being the most costly. This classic study used flight costs that were estimated in controlled conditions, drawing on early results from wind tunnels, where flight speed was also controlled. However, flight costs and speeds can be profoundly affected by the changing aerial environment. This presentation will first consider how the costs of transport (costs per unit distance) are affected by the wind and the availability of updrafts, using data from GPS units and accelerometers deployed onboard a range of species. Following this, a combination of approaches (free flights and wind tunnel trials) will touch on the role of turbulence in affecting flight power i.e. costs per unit time. Overall, there is mounting evidence that flight costs in birds can be as fluid as the medium they fly in.