BUTLER, L. K.**; ROHWER, S; Burke Museum, University of Washington, Seattle; Burke Museum, University of Washington, Seattle: Correlations between flight demands and the structure of contour feathers in small birds

Many studies have illustrated adaptations in birds to reduce the large aerodynamic and metabolic costs of flight, but no study has examined the relationship between flight demands and the morphology of the body feathers that form the plumage surface. We performed two phylogenetically-controlled comparisons between flight and the macro-structure of individual contour feathers. We measured variation in the number and arrangement of the barbs, and we compared that variation to flight demands in small birds. We compared feather structure in two ways: 1) between 21 pairs of congeners in which one species is resident and the other species is migratory, and 2) among 28 resident species that differ in the importance of sustained flight for foraging, such as aerial foragers and bark-probers. Based on those categories, greater flight demands were significantly correlated with barbs that were shorter, packed more tightly together, and oriented in a more streamwise (anterior to posterior) direction. Body feather structure could be related to aerodynamic drag, thermoregulation during sustained flight, or another function that is correlated with the flight differences among the species in our sample.