The fish-eating diving ducks

By BILL CHAISSON
Of a Feather
Our commute to work takes us past Gile Pond in Sutton. Three days ago a broad swath of open water appeared, and I saw a single duck floating in it. By Friday morning, nearly the entire pond was ice-free except for a crescent that extended out from the shaded southern shore to a smooth curve perhaps 100 feet from the beach. Floating at the edge of ice was a large white, low-lying bird with a thin bill: a male common merganser.

I was immediately reminded of the arrival of the mergansers on Lake Flower in Saranac Lake two winters ago. The Adirondacks are considerably colder—higher, further north—than this region, and the ice did not begin to melt off the lakes until April, but as soon as it did, the mergansers were there. My ancient “Birds of America” volume, originally published in 1917, describes these birds as lingering in New England through the entire winter, showing up anywhere that the plunge and movement of the water keeps it ice-free.

The common merganser is the biggest of our three species. The males are striking birds with bodies that appear nearly all white when the birds are afloat. The head is a dark, glossy green, and this color extends down the back in thin strip. The tail and rump are gray. These are ducks—members of the family Anatidae—but they do not have “duck bills.” Instead of being spatulate, a merganser bill is cylindrical, serrated, and bright red during the breeding season. While most ducks feed by sieving through mud for tiny invertebrates and by eating aquatic vegetation, mergansers are fish hunters. They chase minnows, chubs, and suckers by diving and swimming after their prey underwater.

Their bill and their overall shape represents an example of convergent evolution. Although unrelated to either the loons or the cormorants, mergansers resemble both, especially the latter. Common loons are larger than common mergansers — 32 inches long compared to 25 — and loon bills are deeper and not serrated. Both birds, however, ride low in the water and have legs placed far back on their bodies, although mergansers are capable of walking on dry land, while loons are not. The legs serve as rudders in their underwater pursuit of prey, which is propelled by their wings.

In the late summer male mergansers molt into a plumage that is gray overall with a rusty red head. In this season they very much resemble the female of the species, and they look more like loons, which also molt into an overall gray plumage for the winter. Both of these species, which breed on many of the same lakes in New England, tend to show up in coastal salt-water habitats during the winter. However, by November the male mergansers have molted back into their breeding plumage.

It is during the winter that you will see mergansers among the cormorants, although the latter are again larger (33 inches long) and black (although juvenile birds are dark grayish brown). The bill of a cormorant is very similar, but they tend to hold it at an upward angle, while mergansers and loons hold theirs parallel to the water’s surface.

In New Hampshire the common mergansers breed in the Lakes Region, in Coos County, and in scattered locations down to Hillsborough County. The resident birds are joined by the migrants at this time of year, and they collect in large flocks on lakes and rivers throughout the state; this is the southern edge of their breeding range, so many are just passing through. Mating takes place in these large gatherings. Males “chase rivals, rush across the water with slightly raised wings, bob or bow their heads while bill pointing and croaking, and sometimes raise themselves into an erect position. They also display their red feet while churning the water” (according to Arthur Cleveland Bent, 1923).

The red-breasted merganser is smaller than the common and arrives slightly later in the spring. It does not breed in New Hampshire and is seen only in migration; central Maine is the southern edge of its nesting range. It is a smaller (23 inches) and darker bird than the common. While the male common lacks a crest, both sexes of the red-breasted have one (as do the female commons). The smaller merganser shares the green head and red bill with its larger cousin, but its sides are gray, not white, and its breast, though rufous, usually appears dark, except in good light. The white on this species appears in a thin strip above the gray, as broad collar on the neck, and in three squarish blotches in a column behind the chest. The females resemble the common females, but the head is a paler rufous and the bill is thinner.

The most common merganser in New Hampshire is the hooded. It is much smaller than the other two (18 inches) and different enough in appearance to be in its own genus. The males have a broad white crest with a black border, which they raise or lower with changing moods. Much of the head, all of the back and tail are black while the sides are bright rufous red. Two black “spurs” reach down between the rufous sides and the white chest. The only other duck that resembles it is the bufflehead, but they are even smaller (13 inches), their white patch on the head lacks the black border, and the sides are white, not rufous.

As spring progresses you will see each of these mergansers arriving on a pond or lake near you. On a bright, sunny March or early April day they provide a welcome splash of color, and their courtship behavior makes being a duck look like fun.

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.