It was gray and overcast, and roads were slick in spots due to the recent snow and sleet we had received. Temperatures were cold enough to be bracing but not uncomfortable, as long as one kept moving.

My neighbor, Mary Ellen, had a friend’s dog (“Tucker”), to walk and asked me if I’d like to join her.

Sure!” I said. Not only would I enjoy the excursion on its own merits, but I figured I’d get in a little bit of birding along the way. We’d be walking through Bug Light Park in South Portland, which should produce some good seabirds, I hoped.

I wasn’t disappointed. As we turned onto the walkway that paralleled the rocky shore and looked out across Casco Bay, I glimpsed a loon as it struggled with what appeared to be a small crab it had caught.

I called Mary Ellen’s attention to the loon, and we watched as it repositioned the crab in its beak, vigorously shaking it, until it was ready to be swallowed – whole.

Although not a serious birdwatcher, my friend is interested in the birds that she sees, and wanted to study the loon through my binoculars. She was surprised that it was, indeed, a common loon in winter plumage, and not a cormorant, as she had previously assumed.

I described the differences between a cormorant and a loon: loons are pale and two-toned, in coloration, a soft gray above and white below, while cormorants – even juvenile cormorants – are darker. Also, because cormorants are not as buoyant, they sit lower in the water; many times only their heads and necks are visible above the surface. And even at a distance, a loon’s bill is noticeably thicker.

I pointed out, in the loon’s pale plumage, the faintest suggestion of the “necklace” pattern that is one of their prominent identification marks of their full breeding plumage.

Common loons breed on inland lakes and ponds, and migrate to coastal waters come autumn. A loon’s feet are set far back on its body, making it an excellent diver and swimmer; however, this adaptation makes it unable to walk on land. Loons also need at least 30 meters of open water to become airborne, so it’s critical for them to migrate before the onset of serious freeze-up.

As the loon swam farther out into the bay, our attention was caught by a group of four bufflehead ducks. The males were striking in their stark black and white plumage. My friend guessed, correctly, that the darker, drabber birds in the group were females.

This small duck – our smallest diving duck – also utilizes inland lakes and ponds during the breeding season. Unlike the loon, however, this duck can walk on land and does so occasionally. Also unlike the loon – which needs to nest on the ground within a few feet of the waterline – the bufflehead actually nests in tree cavities. It does not excavate its own nest hole, but most often uses the empty cavities of northern flickers and pileated woodpeckers.

The bufflehead’s breeding territory is located primarily throughout Canada and Alaska. It, too, migrates to coastal waters during the winter, giving us a chance to see this beautiful little duck. It’s one of my favorite winter waterfowl, for no matter where I go along the coast, I can almost depend on seeing it. I get a kick out of watching the birds pop to the surface of the water, like corks, after each dive for food.

We watched the birds dive and preen, their presence livening up the forbidding aspect of the gray, ruffled waters of the restless Atlantic. Soon, though, Tucker reminded us of the real reason we were out there – to give him his much-needed exercise.

As we turned our backs on the ducks, I took one more look at the cold, brooding ocean, and marveled at the wonderful adaptability that enabled the birds to live in such an environment.

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