Way out at the entrance to the cove, a lone bird bobbed with the waves. The winter sunlight reflected off it, causing it to shine dazzlingly white. I was ready to dismiss it as a gull – possibly a Bonaparte’s – but Bob Duchesne wasn’t so sure (Bob’s day job includes being a radio announcer with Q106.5 radio, but he is also an active member of the Penobscot Valley Chapter of Maine Audubon, and an experienced birder). He set up his spotting scope.

Within seconds he had made a positive identification – it was a red-throated loon!

These elegant, streamlined loons are not-so-common visitors to our coast in the winter. They are circumpolar breeders – their summer range is restricted to tundra or boreal habitats across North America and Eurasia. In the fall, they migrate southward to coastal areas. In the northeastern United States, the majority of winter sightings occur near Cape May, N.J. More than 8,000 of the birds were seen there on Nov. 14, 1996, and more than 50,000 are counted there every autumn.

Red-throated loons are unusual when compared with other loons. They are small, petite loons that need less flight distance to take off from water, and are reportedly able to take off from land. In contrast, loons such as the larger common loon need at least 90 feet of watery runway to get airborne; if one is forced down into a pond too small or a wet roadway is mistaken for water, it will not be able to take off again.

These loons also differ in the sound department; whereas other loons have four vocalizations, red-throateds have nine different calls. Their primary call is appropriately called the “Plesiosaur call,” (analogous to the “yodel call” given by other loons such as the common loon), and serves as a courtship and territorial advertisement, as well as a reaffirmation of the bond between mated pairs. Here is where they yet again differ: while this type of vocalization is only given by the males of other loon species, the Plesiosaur call is given by both male and female red-throated loons.

Incidentally, this prehistoric-sounding call has been described as “hideous and far-carrying,” by one researcher. And we thought our common loon’s wolf-like wail was eerie!

Red-throated loons have yet a few more differences. They molt their flight feathers in the fall, instead of mid-to-late winter as do other loons. You may also recall a popular depiction of the common loon – both in photographs and illustrations – of small chicks riding on an adult bird’s back. Researchers have never observed this with red-throated loon chicks and their parents.

Lastly – and most obviously – red-throated loons are the most unique in appearance. Whereas the other loons (common, Pacific, yellow-billed, and Arctic) have similar patterns of black and white, the red-throated loon has a steel-gray head and neck with a patch of cinnamon on its throat. Their backs lack the striking checkerboard pattern of other loons, exhibiting only a slight speckling instead. Even their winter plumage sets them apart. Remember that I mentioned how white the bird we saw looked? No other loon is as light in color in the winter.

Chris Corio, a volunteer at Fields Pond Nature Center in Holden, can be reached at fieldspond@juno.com