Laura Erickson's For the Birds

![Loon] (https://farm7.staticflickr.com/6134/6199517738_050a7a10eb_b.jpg “Common Loon”)

(Recording of a Common Loon)

One of the constants of Christmas in the Northland is loon presents. You can find loon books, recordings, stationery, calendars, address books, jewelry, aprons, sweatshirts and t-shirts, neckties, wind socks, bumper stickers, wrapping paper, door knockers, beer mugs and whiskey glasses–all in all, if you managed to get through the entire holiday week without getting or giving a single loony gift, you’re a rare bird indeed. Yet these items are virtually unknown in the southern United States, even though loons spend half of their lives down there.

The loon is uniquely special to north country. The wonderfully exotic plumage, combined with its incomparable voice, are the two features that most people up here equate with the word “loon”–and those two features are exactly the ones the loon loses when it heads to the coast for the winter. All winter, the loon is drab gray and silent. It even loses all its primary and secondary feathers simultaneously in late winter. The new plumage will be in perfect condition for the long flight to Wisconsin and Minnesota in spring, but meanwhile the loon must endure a flightless, vulnerable period on the ocean, where oil spills and pollutants take a heavy toll. Even a clean saltwater environment probably stresses a loon’s physiology somewhat, although it does have salt glands under the skin above each eye to secrete excess salt, keeping the blood salinity at about a third the level of the ocean.

The Common Loon is a perfectly adapted diver–the British Ornithologists’ Union even officially calls it the Great Northern Diver. It catches fish in dives that last about a minute. Although one reputable ornithologist clocked a fifteen minute dive, loons rarely stay submerged longer than three minutes. Many of their bones are solid, unlike duck bones, and so a loon’s specific gravity is just about exactly that of water. Loons can expel air from internal air sacs and can squeeze the air out of their feathers to sink slowly and quietly below the surface, leaving scarcely a ripple. In deep dives, a loon’s heart rate drops, and special physiological adaptations prevent it from suffering oxygen deprivation or developing “the bends” when it resurfaces. The eyes of a loon are ruby red because of a pigment in the retina that filters light, allowing it to see under water. Loons usually use their feet only in swimming, but can use their wings for quick spurts or turning underwater. There are reports of loons caught in nets as deep as 265 feet, although some ornithologists believe dives deeper than about 100 feet are probably fishermen’s tall tales.

Loons eat fish, which they always swallow whole. Small fish are usually eaten underwater, but they bring large or spiny ones to the surface to swallow. Naturally, they gulp the fish down head first, so the scales will slide down the throat as smoothly as possible. Loons can handle surprisingly large fish with their elastic esophagus, although more than one has been found dead with a two-pound walleye stuck in its gullet.

Loons begin returning to Minnesota in late March–migration peaks around April 23. But even if they’re gone for the winter, at least we have our Christmas loon refrigerator magnets as reminders of spring and summer days to come. (Recording of a Common Loon)

This is Laura Erickson, and this program has been “For the Birds.”