The Reason Why Water Rolls Off a Duck’s Back

A viscid episode of KQED Deep Look takes a look at the old saying “like water off a duck’s back” and proceeds to explain exactly the physiological reasons why this adage is quite literally accurate. They go over the difference between down and feathers, how their feathers make ducks, geese, and other birds water repellent, and how the uropygial gland, which sits above their tail feathers, allows the birds to make themselves completely waterproof as they groom.

Ducks and geese spend *a lot* of time preening their all-weather feathers. This obsessive grooming – and a little styling wax from a hidden spot on their backside – maintains the microscopic feather structure that keeps them warm and dry in frigid waters.