Marine Ducks and Geese
Heading out of almost any harbor, in almost any season, a trip to Stellwagen Bank will likely involve marine ducks or geese. The term “marine ducks” is not a scientific term but, describes any species of bird in the Anatidae family (that also includes geese) that makes use of coastal and marine habitats at some point during the year. Like most of the birds of Stellwagen, marine ducks and geese are migratory and are found on the Bank and surrounding waters only seasonally.
Strong fliers and good divers, marine ducks are built to withstand the rigors of the sea. Protected by fine down and oil covered feathers, these species are well insulated from cold winds and water (the feathers trap a layer of air that is warmed by heat lost from the body). Like all members of their family, these animals have broad, webbed feet, set well back on their bodies for swimming, both above and below, the waterline.
Despite a very similar body design, each of the species is recognizable by differences in plumage and, most notably, in the design of the bill. From the stout bill of the shellfish-grabbing scoters, to the long, serrated bill of the fishing mergansers or the short, snipping bill of the brant grazing on eel grass, the bill may be the strongest indicator of how the bird lives its life.
The diversity of this family increases during the winter months when flocks move south from their more northern breeding grounds. Most nest on coastal or tundra habitats of the Arctic and winter in offshore environments further south.
The species descriptions below are somewhat arbitrary. Certainly, many species of duck, including the well known mallard and black, could show up in a bay. Included here are birds that are obligatory marine or coastal habitat denizens – they are superbly adapted to and require the tough life of the sea. Most are likely to be seen during the journey to the Bank – not necessarily on the Bank itself.
Common eider, Somateria mollissima, are one of the heaviest ducks in the area and among the least confusing to identify (at least the males). Built like a tank, their stout bodies help conserve heat and allow them to withstand the rigors of deep dives. Their bills are short, flat and powered by thick muscles allowing them to extract well protected shelfish. Females are covered in rich, brown colored feathers (for camouflage on the nest) while the males are decked out in white and black with faint washes of olive green on the neck and bill. Juvenal plumage can be tricky, with varying patches of brown, black and white (eiders take three years to reach adult plumage). Nesting females pluck pale, soft down from their breasts to insulate their nests – these same nests are collected for the eider down industry (new nests are then made by the females).
After breeding in the north (between the Arctic and coastal Maine) huge flocks gather in protected bays to feed for the winter. Using both wings and feet, eiders may dive to 150 feet and hold their breath for a few minutes. At the bottom, they pluck shellfish (clams, mussels, snails) from the substrate and bob back to the surface. Shellfish are generally swallowed whole and crushed by powerful stomach muscles. Gulls may attend feeding rafts of eiders, picking up bits of food as the ducks resurface. They often form rigid, V-shaped flocks that fly low to the water.
Scoters: surf scoter, Melanitta perspicillata; white-winged scoter, M. fusca and black scoter, M. nigra. All three of these species can be found in our area after leaving their nesting grounds of the far north. These are heavy birds, built for diving and rough seas. In all, the females are dark brown and quite similar in appearance. Males are black with varying patches of white that are diagnostic between the species.
The three species tend to concentrate their feeding efforts in different habitats, loosely based upon depth: surf scoters in the surf zone; white-wings offshore in water up to fifty feet deep and the blacks, much rarer in our area, on offshore, rocky reefs. All hunt mollusks and crustaceans, tearing them from sand or rock. They may form massive flocks and rafts, sometimes by the thousands, in good feeding areas. The three species are best distinguished by focussing on the males. Surfs have swollen, multi-colored bills and white patches on the back of the neck and on the forehead (in some regions they have gained the nickname, “poor mans puffin”). White-wings have obvious wing patches (on females as well) and a white crescent about the eye. Black scoters are entirely black with a bright yellow knob at the base of the bill.
Oldsquaw, are a beautiful species of duck often found in saltwater habitats during the winter months. Like other diving ducks, their compact, heavy bodies, driven by feet and wings propel them to great depths to search for shellfish. Oldsquaw, now officilly called the long-tailed duck, are relatively small, with incredibly long middle tail feathers and complicated plumage pattern. In Cape Cod Bay, they often move in small groups that tend to be quite vociferous, their kazoo-like calls ringing out accross the water.
Bufflehead, Bucephala albeola, are among the smallest of the ducks in our area (13-15” or 33-38 cm). Their high or bluff foreheads,stubby bill and compact bodies give them a distinctive toy-like appearance as the bob on the waves. Like most birds in this family, buffleheads are coastal animals, not pelagic.
Mergansers, including common and red-breasted, are specialized ducks built for pursuit diving. They tend to be active, nervous birds, well-designed for chasing fast swimming fish. Their unusual, long and narrow bills are serrated for extra grip on slippery prey. The common merganser tends to be more common on relatively unprotected, saltwater habitats while the hooded may frequent salt and freshwater marshes. The elaborate courtship behavior of the common merganser is one of the sure signs of pelagic spring. While the drakes contort their bodies for competition, right whales often begin their migration out of Cape Cod Bay while humpback numbers begin to pick up on Stellwagen.
Geese. The only geese likely to be spotted on Stellwagen Bank are high flying flocks of Canada geese or snow geese. Snow geese are often overlooked by whale-watchers that have their eyes trained on the water. During the later trips of fall, take momentary glances to the sky: masses of mostly white snow geese may be seen.
The brant, Branta branta, is the only goose that is likely to be encountered in coastal environments with any regularity. Look for these small geese on the way out for a whale-watch in late fall. Much smaller than a Canada goose, these dainty birds are specialists upon eel grass, a productive flowering plant of shallow bays and sandy flats. After breeding on the tundra much farther north, many flocks spend the winter months grazing the shallows of protected bays and inlets. In flight, they fly in less rigid formation than most other geese in our area.