Why Does a Duck Stay Dry?

Step 1 of 5

The feathers zip shut.

Each feather has rows of tiny hooks that clip into the row beside it, like a zip. Zipped up, the surface has no gaps big enough for a water drop to push through.

Step 2 of 5

Then it is oiled.

A gland near the tail makes an oil the duck combs through its feathers with its beak. Water will not stick to the oiled surface, so it beads and rolls off instead of soaking in.

Step 3 of 5

Underneath is trapped air.

Below the smooth outer layer is a thick fluff of down that holds a layer of air against the skin. Air is a poor conductor of heat, so the cold water never touches the duck.

Step 4 of 5

The feet are cold and that is the point.

Warm blood going down to the feet runs right alongside cold blood coming back and hands over its heat. The blood returns already warm, and the feet sit near freezing without costing the duck anything.

Step 5 of 5

A wet duck is a cold duck.

Preening is not tidiness. A duck that cannot oil its feathers gets waterlogged, loses the trapped air and chills fast, which is why oil spills are so dangerous to water birds.

Down from ducks and geese is still the warmest filling for a coat, for exactly the reason it works on the bird: it traps a lot of air for very little weight.