Structure and mechanics of water-holding feathers of Namaqua sandgrouse ( Pterocles namaqua )

Desert sandgrouse, such as the Namaqua sandgrouse, nest up to 30 km away from watering holes. Adult male desert sandgrouse have specially adapted feathers on their bellies that hold water, even during flight, allowing the birds to transport water back to the chicks at the nest. The structure of the belly feathers and aspects of the mechanism by which they hold water was first described by Cade and Maclean (Cade, Maclean 1967 , 323-343 (doi:10.2307/1366197)). Here, we use scanning electron microscopy and micro-computed tomography as well as videography to characterize the geometry of different components of the belly feathers and to show how differences in their bending stiffnesses contribute to the water-holding mechanism. The results of this study will be used in a companion paper to model computationally water uptake by the feather.