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Résumé :
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The water transport of sandgrouse (Pteroclidae) presents one of the most amazing behaviors in birds. The unique ability to absorb water by their abdominal feathers was disclaimed over decades but is described here for the first time. For a comprehensive picture of the morphological and physical parameters, we used different approaches in pterylography, functional morphology, biomechanics, new measurement techniques and calculations of wetting properties, absorption capacity tests and numerical simulations. We show that the ability of carrying large amounts of water is caused by different factors like: the distribution of feathers on the underside, a specialized feather margin, a well-directed hygroscopic alteration of the microstructure, which is the first discovered in the animal kingdom and a unique hydrophilicity of the feather material. Determination of absorption capacities of feathers in sandgrouse and non-sandgrouse species clearly shows the effects of the different adaptations in feather structure. Numerical simulations determine the adhesive force of the feather microstructure of sandgrouse and show that minimal changes of the structure lead to a complete loss of the specialized properties. From this we conclude that the microstructure of sandgrouse feathers has evolved to absorb the largest possible volume of water with as little material as possible. Our results show that the water transport in sandgrouse is based on the interaction of many highly derived characteristics.
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