Meeting Abstract
Flight performance is a critical aspect of avian biology. However, few studies have yet addressed the impacts of wing coloration on birds’ flight. Dark colors are known to absorb more solar radiation than light colors, which would lead to a faster increase in surface temperature. A warmer dorsal wing surface could lead to decreases in air density above the wing and in turn decrease the drag. Yet, solar heat gain can be extremely sensitive to changes in wind speed, which in our case resembles the flight speed. In this study, we tested the prediction that darker wings, that are exposed to the direct radiation of the sun, heat up to higher temperatures than brighter wings. We further suggest that the temperature difference would persist even during flight, hence including high aerial convection rates. We tested the impact of solar energy and flight speed on the surface temperatures of differently colored wings in three steps: 1) We modeled the temperatures for altering solar radiation intensities and wind speeds. 2) We took reflectance measurements and thermal images of live birds that were exposed to changing intensities of solar radiation to compare those temperatures with our predicted values. 3) We exposed differently colored stuffed wings in a wind tunnel and measured their surface temperatures for altering radiation intensities and wind speeds. The heating experiment in the wind tunnel served as a sensitivity analysis to test the interactions of various factors during flight: The impact of solar radiation, wind and wing coloration on wing surface temperature as well as the impact of wing surface temperature on air density above the wing. With this study we want to show to what extend flight is affected by wing coloration, solar radiation and flight speed. Thereby we may address a new important factor in avian flight and migration.
