By Bill Chaisson
There is a stretch of Village Road in Wilmot Flat where you drive across a small causeway between Tannery Pond and a smaller body of water that has recently been flooded and expanded by beavers. Local folks say that separation has always been there, but the geologist in me sort of doubts it. Historically, this little height of land is all that lies between two branches of Cascade Brook. One branch comes out of Pleasant Lake in New London and the other comes off the side of Mount Kearsarge and out of the morass of the Low Plain, an area where the icesheet dumped random piles of sand and gravel.
Wilmot Flat is as flat as it is because the bottom of the valley between Kearsarge and the slope up to the hills of North Wilmot is full of glacial outwash. Brooks have been wandering across the flat for 10,000 years, cutting through the sand and redepositing it downstream. For just about as long, I am sure beavers have been damming these brooks and backing them up into ponds until the next 100-year flood washes out the dam. Those ponds are where generations of hooded mergansers (and other pond ducks) have made their homes.
In the 19th century, local entrepreneurs built more permanent dams on the branch of Cascade Brook that leaves Pleasant Lake. The lake itself is created by a berm in Elkins, and other dams downstream hold back Chase and Tannery ponds. You see this brook called the Blackwater River on a lot of surveyors’ plans, but the USGS says otherwise and their topographic maps preserve the piece of Cascade Brook that flows into Pleasant Lake from the south. Before there was a lake there, it just turned right and flowed through Elkins.
The ducks don’t really care whether 19th-century entrepreneurs or beavers built the dams; they just like the ponds. About two months ago I began seeing a group of five dingy-looking ducks floating on Tannery Pond. The beaver pond was full of mallards, but when I stopped my truck and got out my binoculars to take a look at the dingy ducks, they dove.
They didn’t stay down for very long, and when they popped up again, they weren’t far from where they’d gone under. They were nervous about my presence, but not that nervous. I stayed still, my eyes glued to the binoculars, making fine adjustments to the focus to see these nondescript birds as well as I could. Their feathers were a few different shades of brown, darkest on the back and wings, lighter along the sides, and lightest on the breast. They all had ragged crests, which they kept down, not quite flattened, and this showed the only real color on the birds: a faint blush of rufous. The bills were very thin and light colored.
These were juvenile hooded mergansers, perhaps a single brood, spending their first fall hanging around and learning to fish on Tannery Pond, just as generations of their ancestors did before them. As the weeks went by, I saw them frequently. Their numbers varied—because the pond is an impounded brook it winds out of sight in a couple of directions—but generally the little flock got smaller and then disappeared a few weeks ago.
Two weeks ago, I began seeing another pair of ducks on the pond. These were easier to identify. The adult male hooded merganser is a striking bird; one of its vernacular names is “water pheasant.” If I had better light, better binoculars, and maybe just a longer attention span, I might have spotted him in the flock in September, where he would have been identifiable by a darker bill and a lack of rufous blush on the head.
The head of a male hooded merganser is sometimes confused with that of the bufflehead, another diving duck. They both have a large fan of white spread out behind the eye on what appears to be an otherwise black head. The bufflehead is much smaller (only 13-14 inches long), has a purple gloss to its black head, and lacks the thin rim of black at the outer edge of its fan. And its stubby spatulate bill is a light blue-gray, while the merganser’s is black.
The male ducks were still in their eclipse plumage two months ago, that dull suit of clothes they put on after breeding. In September they molt back into breeding plumage, regaining their flashy looks and their powers of flight. The females also molt, but they always resemble the juvenile birds.
The hooded merganser has a white breast split on either side by black “spurs” that dive down into the water from a black chest. This feature gives them another vernacular name, the pick-ax sheldrake. All mergansers are referred to as “sheldrakes” because they generally resemble a group of European ducks by that name.
Hooded mergansers (Lophodytes cucullatus) aren’t related to shelducks, and they aren’t that closely related to the common (Mergus merganser) or red-breasted (Mergus serrator) mergansers. In the 1940s no less a personage than Ernst Mayr proposed merging the merganser and bufflehead-goldeneye subfamilies. The only consistent anatomical difference between them is the thin, serrated bill of the mergansers. It is an adaptive feature, and so is not a good means of classification. Frequent hybridization between members of the two families is also well documented. There is also frequent brood parasitism among them. And, unusual among ducks, most members of the mergansers and bufflehead-goldeneye group nest in hollow trees.
The hooded mergansers migrate, or rather roam, only to stay on open water. When I drove by last week during a cold snap, there was a skim of ice on Tannery Pond, and they were gone.
Bill Chaisson, who has been a birdwatcher since age 11, is a former editor of the Eagle Times. He now works for the Town of Wilmot and lives in Sutton.