One part of the study investigates the aerodynamic characteristics of the separated feathers that form slots at the wing tips of birds that soar over land. Theoretically, these feathers could reduce air resistance (drag). Similar structures (winglets) on the wing tips of some modern aircraft have this effect. The study will measure how much the tip feathers reduce drag in living birds and model bird wings in a wind tunnel. The results will answer a long-standing question about the role of the tip feathers in birds and will provide data that can be compared with measurements on aircraft winglets. A second part of the study investigates the drag of wingless birds in a wind tunnel. Body drag must be known in order to evaluate theories for both gliding and flapping flight. These theories explain how birds fly, and they are used to calculate food requirements during both daily foraging and long migratory flights. The amount of food that an environment can supply is a factor that must be considered in any plan to maintain or restore bird populations.
