Each morning, upon waking, I gaze out my third-story bedroom window to enjoy the sun rising over Casco Bay.

On one particular morning a week ago, the view was especially beautiful: The sky was perfectly clear, yet the air over the ocean was slightly misty. A silvery gold sheen came off the surface of the water, which was flat calm, and the tide was out.

On impulse, I opened the window to get a breath of fresh air to alleviate the dry stuffiness of my heated apartment and was immediately greeted with the spine-tingling calls of loons.

It appeared the calls were being made by at least two loons, if not more. The wavering tremolos continued unabated for up to 30 seconds, and I wondered what was setting the birds off: the presence of others of their own kind or the human activity on the beach – it was hard to tell.

No matter the reason, the wild sound electrified the cold morning and made the misty tableau seem even more surreal. It hinted at the spring season passed, conjuring up images of fog-shrouded lakes where the loons go to mate and raise young.

The calls stopped, yet the spell lingered. But I began to notice the nip in the air and reluctantly closed the window. I tried not to think how far away spring was at that moment.

I wasn’t surprised at the loons’ presence on the bay, as they migrate here from inland lakes and ponds after the breeding season. Superbly adapted to their environment, they’ll spend all winter in the frigid waters along the coast. They catch their main food – fish – by diving as much as 75 meters below the surface; they can stay under for as long as eight minutes.

Everything about the loon streamlines it for pursuit of fish in its aquatic environment. Its primary means of propulsion – the legs – are set far back on its body and are laterally flattened, offering little resistance as the bird darts after prey. The feet are large and, of course, webbed. Less obvious characteristics include denser bones than those of other birds; this facilitates diving. They also have exceptionally dense plumage which keeps them warm and waterproof. I was surprised to hear them so vocal, though. Loons have three main calls: the wail, which resembles a wolf’s howl; the yodel; and the tremolo, which is often referred to as the loon’s “laugh.” Each call has a specific purpose and context in which it is used.

The yodel is a territorial call and is given only by males. It is used in defense and also during aggressive acts towards other males.

The wail is used by both male and female loons as a means for the birds to stay in touch.

The tremolo call is often used in moments of distress, either because of antagonistic encounters with other loons or by outside disturbances. This was the call I thought I was hearing that morning, but I was too far away to determine the cause.

As the season progresses, I know I’ll see more of the birds in our protected bay, as well as anywhere along the Maine coast. I hope I’m blessed with hearing their wild and eerie call again soon.

bdnsports@bangordailynews.net