Most people in the Chesapeake Bay watershed are not familiar with loons. Yet two species — the common loon and red-throated loon — can be spotted here during the winter months.

Loons are the submarines of the bird world. Webbed feet gracefully propel this bird underwater, giving the impression of submerged flight, as the bird stalks its prey. Diving, sometimes as deep as 200 feet, the loon snatches a fish in its dagger-like bill and returns to the surface to eat.

Recognized by sleek bodies, thick necks and short tails, loons float low in the water and can easily ride out the fiercest storms. They spend most of their lives on the water. Feet located toward the rear of their body make loons agile in water but awkward on land. They only come ashore to breed or when wounded.

Though secretive and wary of humans, the loon’s high-pitched wails, wild laughter and mournful yodels pierce the northern air, revealing the bird’s position. Loons breed in freshwater ponds and slow rivers of the arctic and subarctic reaches of North America. Near the shoreline, loons fashion their nests from aquatic vegetation.

Red-throated loons are the most northern breeder, found from British Columbia in the west to Newfoundland on the Atlantic coast. The most southern breeder is the common loon, breeding from Alaska and northern Canada south to the Great Lakes region and New Hampshire.

Because of their dependence on water, loons must migrate to ice-free areas during fall and winter.

In flight, a loon’s neck curves slightly downward, giving it a hunchbacked appearance. They are swift and powerful fliers, usually migrating singly or in small groups. Loons begin their southern migration before nearby waters freeze, sometimes as early as August. On the East Coast, loons winter from New England to the Gulf Coast, including the Chesapeake Bay. Loons begin arriving in the mid-Atlantic region from mid to late October.

Their dull winter colors camouflage them as they brave the frigid waters of the Chesapeake. When people think of loons, it is the common loon that first comes to mind. During the breeding season, a common loon is easily identified by the black and white collar around its neck, black head and bill, and black-and-white spotted back.

When wintering on the Chesapeake Bay, common loons are not very noticeable as their colors have changed to a dull gray head, neck and back with white cheeks, throat and breast. Wintering common loons feed primarily on fish and during the day. They hunt in individual territories but often gather in groups, known as rafts, at night. By late autumn, most common loons are found along the shoreline from the mid-Bay region south to Virginia.

Red-throated loons wintering on the Chesapeake Bay are rare sights as they prefer deeper waters and stay farther away from shore. Smaller than the common loon, the red-throated loon has a slightly upturned bill and red eyes. During breeding, the red-throated loon has a gray head, white cheeks, red throat patch and black-and-white speckled back. Horizontal black and white stripes adorn the back of the neck.

In winter, the head and body are brownish-gray and the throat is white. The red-throated loon’s call, though seldom heard, is a high-pitched wail. It is the only loon that can take flight directly from water, springing into the air. All other loons must run along the water’s surface before taking flight.

Like the common loon, red-throated loons are powerful fliers. During migration, red-throated loons fly a mile or two from land, usually alone. They may call to one another on foggy days to help maintain the flight path.

More sociable then other loons, red-throated loons often gather in groups during winter feeding. By December, most red-throated loons on the Chesapeake are dispersed from the Potomac River south to the mouth of the Bay.

If you are out on the Chesapeake during the winter or trekking along the shoreline, look out across the water. You may catch a glimpse of a loon riding the crest of a rough wave then disappearing into the trough. Be patient. It will reappear on the next wave.

Listen carefully and you may hear its call. The mournful wail gives the impression of homesickness. Perhaps the loon is lamenting its temporary exile from the placid ponds of the northern forests. By March, the instinct to migrate will urge the birds to migrate back to familiar nesting areas.