How an African bird might inspire a better water bottle

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How an African bird might inspire a better water bottle

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  Condor 69 , 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.

1. Introduction

Namaqua sandgrouse ( Pterocles namaqua ) are found at the edges of deserts, among short grasses and occasional shrubs, in South Africa, Botswana and Namibia. They feed primarily on dry seeds, with infrequent insects. Pairs nest on the ground, typically within 10 km, but up to 25–30 km, of a watering hole. Chicks are precocious, able to walk an hour after birth, but unable to fly for the first month; in particular, they are unable to fly to the watering holes where the adults drink. Instead, adult males transport water back to the chicks in their belly feathers (figure 1 a , b ). This remarkable behaviour is shared among all 16 species of desert sandgrouse (family Pteroclidae) except for the Tibetan sandgrouse ( Syrrhaptes tibetanus ), which live in the steppes of central Asia [1,2].

Figure 1.

Figure 1. Male adult Namaqua sandgrouse ( a ) before and ( b ) after soaking their specialized belly feathers in water. The arrows indicate the regions that hold water. Photos reprinted with permission from Hugh Chittenden. ( c ) The specialized feathers occur in the belly region of the bird; the dashed envelopes indicate the regions that hold water. ( c ) Specimen no. 142928, Museum of Comparative Zoology, Harvard University © President and Fellows of Harvard College. Scale bar = 50 mm.

An extreme closeup of feathers from a bird with an uncanny ability to hold water while it flies could inspire the next generation of absorbent materials.

With high resolution microscopes and 3D technology, researchers at Johns Hopkins University and Massachusetts Institute of Technology captured an unprecedented view of feathers from the desert-dwelling sandgrouse, showcasing the singular architecture of their feathers and revealing for the first time how they can hold so much water.

"It's super fascinating to see how nature managed to create structures so perfectly efficient to take in and hold water," said co-author Jochen Mueller, an assistant professor in Johns Hopkins' Department of Civil and Systems Engineering, who specializes in smart materials and design. "From an engineering perspective, we think the findings could lead to new bio-inspired creations."

The work is published today in  The Royal Society Interface .