Mechanics Of Flight Feathers: Effects Of Captivity?

Feathers act as aerodynamic cantilevers, and to withstand the prolonged cyclical loading that occurs during flight, feathers must be stiff, lightweight and strong. We experimentally tested the differences in feather structure, primarily stiffness and size, between (a) wild and captive Barnacle Geese Branta leucopsis, and (b) primary feathers dropped during the annual flight feather moult, and those feathers freshly regrown during the moult process. We found that, despite having undergone a 5,000km round-trip migration, flight feathers dropped during moult in the wild geese were stiffer than those measured in the captive geese, both for those dropped during moult and those re-grown. We propose that this may be related to diet or stress in the captive geese.