This is Bird Note.

To hear a common loon in the wild during the summer, you'll need to find a northern freshwater lake where a pair is nesting. But to find that same common loon in winter, you'll likely need to look on a saltwater bay. Oh! Ah!

Ah! In the sea one loon in winter, you'll likely need to look on a saltwater bay.

The shift from fresh to salt water would kill most animals, but loons, along with many ducks

and other water birds, have evolved to be able to make that move. When a loon starts ingesting prey in water

that's high in salt, that salt gets into its bloodstream. This sets off a complex physiological

process that reaches its end point in a pair of glands above the eyes. These glands, also activated

by the higher salt levels in the body, excrete the

excess salt through a duct that leads to the bird's nostrils. From there, the salty

solution runs down the beak and back into the environment. When switched on, the salt glands

burn up a lot of calories.

So it's possible that breeding adults nest on freshwater to save that energy for raising chicks.

But most of these areas start to freeze over come late fall.

And then it's time to seek a watery place that won't freeze.

A salty one, like the Gulf of Mexico, or Puget Sound.

For Bird Note, I'm Michael Stein.