Yesterday morning, the house felt chilly, so to warm up I decided to go outside and walk around the yard. I knew a bit of exercise would warm me up, and that after being out in the cold air the house would feel toasty by comparison. As I walked toward the lake I glanced over to where the neighborhood mallards often gather in the south cove, but something about the birds there made me take a second look. They were too white. I looked through my binoculars and saw they were common mergansers.

In December, the arrival of flocks of common mergansers on the lake signals that the lake will soon freeze. Sometimes, I see only a few mergansers, at other times the flocks can be quite large, and one year I counted 273 in a single flock. The mergansers in the south cove began to move slowly out toward the open lake. A few birds swam back toward the rear of the flock, and a few milled around in various directions, but I managed to count one hundred twenty of them before they all began to dive for fish. Watching these large birds riding low in the water I could see why folks occasionally mistake them for loons, but at this time of year loons are in their dull gray and white winter plumage. Male common mergansers, which are smaller than loons, are bright white, with a black head that in certain light can appear dark green. Female common mergansers are gray, with a rusty brown head and a shaggy crest. Mergansers are not related to loons, they are related to ducks, and are the only North American members of that family who specialize in eating fish. Their distinctively thin, bright orange-red serrated bills are perfect for catching and holding slippery fish.

Common mergansers are typically found on clear fresh water lakes and rivers, where they nest in holes in large trees, in holes under tree roots, or in crevices among rocks. They are holarctic, which means they breed in northern areas around the globe. Those who migrate through our area probably nested somewhere within the region that extends from northern New England and the Maritimes, to the Labrador coast, throughout Newfoundland and across the Province of Quebec. Their North American wintering grounds extend from southern New England and the Carolinas to the Pacific Ocean.

The flock of common mergansers on our lake appeared to be relaxed, and I could hear them murmuring softly to one another. If they were moving south just ahead of freezing lakes they did not look as if they were in a hurry, but I knew their presence on our lake was a sign that very soon the lake would be locked in ice. For several days, patches of ice had been drifting around the lake, and close to shore a thin sheet of daintily patterned ice pulsed gently up and down with the motion of the water. A few big rocks along the shore wore a shield of ice on their tops, and twigs overhanging the water were laden with oddly shaped clumps of icicles. One thin twig that stuck up from below the surface of the water was topped with a perfectly rounded bulb of ice, making me think of a lovely water lily blossom made of blown glass.

At the end of my walk around the backyard yesterday morning, I felt much warmer, and when I returned to the house it felt toasty. Then during the night, cold, still air settled on the lake, and this morning the first thing I saw out the window was that the entire surface of the lake was frozen. There was not a merganser in sight.

The annual Christmas Bird Count is scheduled for Tuesday, Dec. 28. Folks who live within the 15-mile wide Count Circle can help by keeping bird feeders filled that day (and a few days prior) to attract birds. If you wish to participate in the count call 647-2847 before Dec. 21 for more information and brief instructions.