Meeting Abstract
Birds are known to exploit global airflows; adapting their migratory routes to reduce the high energy costs associated with long distance flight. It would follow that birds also modulate their flight behavior at fine scales as well, however due to the stochastic nature of the fine scale environment these behaviors remain unknown. We investigated the flight behaviors of herring gulls (Larus argentatus) and lesser black-backed gulls (L. fuscus) in Swansea Bay, UK, where these gulls are often seen commuting along the urbanized seafront. There was significantly more gull traffic on days where wind conditions generated orographic lift in front of a row of three story hotels. The gulls were clearly exploiting the airflows around these seafront buildings so, in order to understand the aerodynamics involved we developed a model of the wind field in which the gulls were flying. The fine scale wind model of the urbanized beach was developed using computational fluid dynamics (CFD). When we added the flight trajectories to the wind model not only did we discover that gulls indeed change their flight paths to make use of the available wind energy, we also found adaptive flight strategies within this. The strategy appears to result in a self-regulating control phenomenon where gusts have a reduced effect on the bird’s airspeed. We hypothesis that this behavior improves flight control in turbulent conditions and mitigates the risk of collision in a cluttered cityscape. Overall this study shows that gulls adaptively modulate their flight paths in relation to fine scale wind features created by urban development and opens up questions as to how birds utilize other fine scale wind flows.
