Sandgrouse’s feathers function like a sponge, high-resolution images show. The sandgrouse has tightly coiled filaments in its feathers, which unfurl when wet to trap water.
A close-up of a desert bird’s belly feathers revealed complex, coiled structures that absorb and hold water. So can the Namaqua Sandgrouse (Pterocles namaqua) carry water in its plumage.
Male Sandgrouses make daily trips to wetlands in South Africa. There they soak their belly feathers in the water. Engorged with moisture, they fly back to their young, up to thirty kilometers away. There the thirsty chicks suck the water from Daddy’s plumage. More than fifty years ago, researchers discovered that these feathers have coiled filaments called “barbules.” But no one had looked closely at that.
READ ALSO
How healthy is an ice bath?
Exposing yourself briefly to extreme cold is good for body and mind, according to health coaches. More and more people are therefore stepping into an ice bath or …
Smallest detail in plumage exposed
To see these special feathers in detail, researchers used high-resolution microscopes, micro-CT scans and 3D modeling technology, among other things. They found a stiff central spring shaft that supports symmetrical rows of barbs: the ‘side branches’ of a spring. The beards are covered with coiled ‘barbules’, a structure that most closely resembles ferns with curled leaves. When they dipped the feathers in the water, the researchers saw how the curled barbules sucked in water through their capillary action.
“As soon as the barbules get wet, they roll out and form a kind of thick forest of straight barbules, which is what holds the water in the spring,” says engineer Jochen Mueller from Johns Hopkins University in Maryland, USA. The best part is that it’s reversible. As soon as the water is out and the feathers are dry, they roll up again.’
Based on previous research, Mueller had already expected these curled barbules, but the researcher found that the barbules also grow directly from the central shaft. Together with his colleagues, he also saw a honeycomb-like structure in the central spring shaft, which makes the shaft lightweight and sturdy.
Feathers inspire new technology
“Much of the most exciting science happens when you apply new technology to investigate long-known biological systems. The belly feathers of the sandgrouse are an excellent example of this,’ says ornithologist Allison Schultz of the Natural History Museum in California, who was not involved in the study.
Mueller hopes that a better understanding of sandgrouse feathers could lead to new technical innovations. Like better ‘cotton swabs’ that you stick up your nose to test for COVID-19. They must absorb liquids efficiently as well as release them efficiently.