Can loons drink salty ocean water?

How do fresh-water birds deal with salty water, like ocean water? We've been following the Common Loons radio-tagged last summer as the birds migrate south for the winter (see post below). The loons currently are eating and drinking in either the Atlantic Ocean or the Gulf of Mexico. Both bodies of water contain roughly three percent salt. One percent is a normal concentration of salt in bird blood. An overdose of salt is poisonous, so how do the loons do it?

Seabirds that never have access to fresh water have a salt gland that removes the salt from ocean water they ingest. The gland is located behind their eyes. In some cases a salty solution drips down the bird's bill. Other species have tubes on their bills through which the salt is removed. At least one species sneezes to drive the salty discharge solution through the tubes.

Do birds we consider fresh-water creatures have salt glands? Yes. The gland is inactive until needed, then swings into action. Loons have these glands as do grebes and ducks and cormorants, among other species. Some species of desert birds, like the roadrunner, have active salt glands because the desert can be a salty place. Prey animals taken by the roadrunner could be salty enough to be a problem.

Passerines – perching birds like our robins, thrushes, warblers, etc. – are the only family of birds that lack salt glands. What if when enjoying winter along southern shores you, as a blackbird, eat salty things? Your kidneys go to work removing the salt.

Take a look at this Northern Fulmar, a seabird species. Look at its bill. The bird is one of several species known as tubenoses, for good reason. Salt removed by the bird's salt gland is blown away through the tubes that sit atop its bill.