A Humboldt Penguin swims underwater. Interlocking hooks on its feathers allow it to swim free of ice. — Interlocking hooks on the feathers of Humboldt Penguins allow the birds to swim free of ice. Photo by Wilfried Wittkowsky (Wikimedia Commons).

Penguins live in the coldest places, yet frost and ice rarely adhere to their body feathers. Why? Scientists once thought the feathers’ ability to shed water was the reason — moisture simply slides off before it can freeze — but research suggests that there’s more to it than that: When humidity is high or temperatures fall really low, ice can stick even to slippery surfaces. So how do penguins do it?

Researchers recently examined Humboldt Penguin feathers using a scanning electron microscope. They found not only a network of barbs, barbules, and miniature interlocking hooks but also “many elaborate wrinkles.” The architecture of the feathers indeed keeps water out, write the scientists in the Journal of Physical Chemistry C, but the tiny grooves are also anti-adhesive, meaning ice doesn’t stick.

Eldon Greij explains the clever way birds keep legs and feet warm.

How Emperor Penguins survive Antarctic cold while holding an egg on their feet.

See reader photos of penguins.

Read the paper

Shuying Wang et al. (2016) Icephobicity of Penguins and an Artificial Replica of Penguin Feather with Air-Infused Hierarchical Rough Structures, The Journal of Physical Chemistry C.

A version of this article appeared in the June 2016 issue of BirdWatching.

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