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Inside the Outdoors: These ducks use a periscope … in reverse

Inside the Outdoors with Mike Rahn

Photo illustration, Shutterstock, Inc.

One of the coincidental benefits of spring ice-out, besides the long-awaited opportunity to fish open water instead of on the ice, is the arrival of so many varieties of water-oriented migratory birds. Most conspicuous are waterfowl: ducks of many species, our state bird, the loon, Canada geese, tundra and trumpeter swans, cormorants—which some condemn as fish-eating villains—and others.

They begin arriving as soon as there is a ribbon of open water along shorelines. They’re most easily seen close-up then, before a lake’s entire surface has lost its covering of ice. But even after lakes become ice-free, many waters host hundreds—at times even thousands—of waterfowl that linger to rest, feed or both. Because spring is the time of breeding, waterfowl are now at their most colorful, as the secondary sexual characteristic of plumage plays an important role in courtship and mating for many species.

One of early arriving migrants that is low on the “edible” list of duck hunters is high on my “interesting” list. The merganser—there are several North American species—is known to hunters by the uncomplimentary name “fish duck.” Mergansers have not been outfitted by Nature with a broad flat bill, like most ducks. Instead, theirs is long and narrow—pencil-like—and both edges of upper and lower mandibles are studded with tooth-like points. They’re perfect for grasping slippery, wriggly prey, like minnows and small fish.

Fish, snails, leeches, mussels, aquatic insects and other non-plant foods make up most of their diet. As we’ve heard often from moms and others concerned with good eating habits, “You are what you eat.” Consequently, mergansers typically have a stronger taste than ducks that dine mostly on wild rice, duck potato, acorns—yes, wood ducks do—and other aquatic plant foods. On the other hand, I’ve eaten mergansers, believing as I do that shooting something carries with it a certain obligation. If it comes to that, there are many ways to temper strong game flavors with the right recipes.

As this is being written, on the first day of May, the ice on the lake where the family cabin has stood since the late 1950’s is perhaps several days from fully disappearing. But there has been open water along our northern shoreline for some time now. Gathering there has been the vanguard of the greater numbers of waterfowl that are expected soon. So far, some Canada geese, mallards, several pairs of goldeneyes and a larger number of common mergansers.


“Common” is a name that bird people should purge from their vocabulary and nomenclature. For starters, what is common in one place may be rare in another. Common also blurs our sense of a bird’s uniqueness, since it is applied to a substantial number of birds: common crow, common loon, common eider, common gallinule, common nighthawk, common yellowthroat, common tern and common redpoll. Need I go on? Common smacks of elitism and snootiness, too. In England, if you are not among the royalty or the gentry, then you are a commoner; certainly not a compliment.

Nevertheless, the by-the-book identity of the waterfowl we’ve seen the most of so far at the cabin this spring is the common merganser. It’s a mallard-size duck, but is notably more streamlined in the body, in the way that a submarine is more tapered in its profile than a fishing trawler or a tugboat. Understandable, because mergansers—all three North American varieties—secure their food by diving beneath the surface.

Under water, being streamlined—“hydrodynamic” is the proper term—is an advantage when chasing down food that can also swim, and would prefer not to be eaten. It’s probably no evolutionary coincidence that loons are also very streamlined in the body, for they feed in the same underwater way, and on some of the same prey.

The common merganser (Mergus merganser) male on the hunt.
Photo illustration, Shutterstock, Inc.

Mergansers and loons share another distinctive behavior. When foraging for food, both will paddle along with their head tilted downward, their bill and eyes submerged to aid in locating swimming prey. This “down periscope” cruising reduces the energy that must be expended while feeding, by not having to spend as much time randomly swimming beneath the surface. You’ll see them—both mergansers and loons—swim along in this way, then suddenly jack-knife their body in a dive beneath the surface.

In addition to this style of fishing, mergansers will also use their slender bills to probe bottom sediments and between stones for less active and elusive prey. Mergansers generally feed in relatively shallow near-shore waters. Loons do, too, but when necessary can they dive to depths of more than 200 feet, and are sometimes entangled in deep-set commercial fishing nets in waters like the Great Lakes.

In addition to the common merganser, also often seen here is the much smaller, wood duck-size hooded merganser—so named for the hood-like, white-on-black crest worn by the male. Less commonly seen here is the red-breasted merganser, which is slightly smaller than the common merganser, but notably larger than the hooded variety.

Both common and red-breasted mergansers nest to the north of us, most heavily in Canada. But while the common subspecies winters widely almost continent-wide, the red-breasted merganser winters mostly along East and West Coasts. As a result, it is less likely to be seen here when migrating northward in spring to nest. Both species prefer to nest in tree cavities, something a bit hard to fathom for birds that are significantly larger than the tree-nesting wood duck or hooded merganser.

The drake common merganser is plumed mostly in black and white—some say tuxedo-like—with a dark green head. The more colorful drake red-breasted merganser has notably less white on its flanks. Its breast, rather than pure white, is reddish and mottled with black streaks. Its head, too, is plumed in dark green.


As with most ducks, the hens of both of these merganser subspecies are much more subtly plumed. The heads of both have spiky, rearward-pointed feathers that some liken to a human cow-lick. Or, at best, a bad hair day! The male red-breasted merganser also has this comical-looking head feathering, something that is not seen to be on the smoothly-plumed head of the drake common merganser.

Mike Rahn - Inside the Outdoors.jpg
Mike Rahn, columnist

As I watched a small band of common mergansers paddling and feeding in the shallows down the hill from the cabin, I noticed a bird that was clearly a male, but also had that tell-tale cow-lick. A closer look through binoculars revealed a drake red-breasted merganser, a bird I seldom see here. Its Latin name, Mergus serrator, says all that’s needed about the way mergansers of all three subspecies feed. If you’re familiar with the small teeth of a serrated steak knife, you might see an obvious resemblance.

That’s bad luck if you’re a minnow or a small fish that one of these ducks spies while doing its version of the periscope drill!

Opinion by Mike Rahn
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